I have been involved in the SB, off and on, for almost exactly one year. I am going to attempt to chronicle my experiences and a few observations. Feel free to join the discussion. First off, since I am married (currently) my approach is likely very different from those that aren't. But, here's my approach. I have a decently worded profile (without photo). I mention in the profile that I am clean cut (Disease and Drug Free, with no tattoos or piercings) and would be happy to send a photo after we've made contact (that is always by private e-mail, and not on the SA site). I make it very clear that me not attaching a photo to my profile is not because of my appearance, but because of my need for discretion.
I'll make some comment in my note to the SB to let them know that I've read their profile. I'll write something like "You might be the perfect combination of brains and beauty" I'd like to speak with you to see if we "Spark" if so, I'm up for grabbing a coffee to see if we have real chemistry. Unlike Z, I never offer a $$$ for an initial meeting, but If the initial meeting goes well, and It's some woman I'm interested in,  I'll have an envelope prepared ($50 per envelope). 60% or so will respond to my initial note. I'll have phone chats with about 40% of them. In my opinion this is crucial. I've saved myself countless hours by talking, before meeting. Here's how:
1.) One woman told me she was 5'3" and 168 lbs. I knew right away she was a Hippo (No thanks!!)
2.) Another lady told me her last arrangement gave her $4,000 per month to start and ended up giving her $10,000
Per month toward the end. Again, no thanks!!
3.) Another lady said on the first call "We don't need to talk, or meet up. I will make you very happy. The entrance fee is $3,000 per month. That is what my monthly bills/expenses are for me and my child" (The next sound was a 'click' from me!!!)

IMO, those calls are crucial and have saved me plenty of time and aggravation. I have a few rules, or at least things I've noticed:
A.) For me, having kids, at least multiple kids, is a deal breaker!! What a buzz kill. The woman will tend to be more serious, needy and have less time for me/you.
B.) My sweet spot is ladies between 24-30. Girls, I said "Girls" that are under 24 I have a very hard time having any meaningful connection with. I am near 50 and immaturity is a huge turn off for me. Again, I tend to appreciate the sex and the connection/time more than just the physical.
C.) All of us are experienced enough to weed out the pros/semi-pros.
D.) Women that are desperate for money (Sob stories) are an obvious "no go".
E.) Since I am married I find it refreshing the number of ladies who won't engage with me because i am committed. But, i am much more impressed with the women who I will
F.) Thank Goodness for bad/clueless boyfriends who make this possible for guys like us!!
G.) I've been surprised, pleasantly, that some of the women actually do want/appreciate advice (in addition to the envelope). I gave my last arrangement girl feedback on her resume, grad school essay and life advice, who knew???

I weed out the losers the same as you do via exchanging messages.  Can't say why, but I'm more comfortable doing it that way.  Different method, similar results. As for your rules, whatever works for you is good.  But here's my comments:
A: Kids are not a big problem.  Those Moms are often more focused and ready to negotiate
B: I'm 69 and my 3 current SBs are 19, 19 and 22.  Their youth and freshness is a huge turn on for me and they are surprisingly thoughtful intelligent young women
C: True, although I've dated a few pros thru SA and have no problem with it.
D: Very true!
E: I'm happily married but we are very polyamorous.  I've had to explain this to several SBs so they know they can date me without enabling a cheater.
F: Yup, very true.  My most recent SB dumped her last worthless BF because he disrespected her expressed desire to live a poly lifestyle.  His loss, my gain.
G: Also delightfully true.  I'm training one of my SBs in financial management,  how to invest and how to plan for retirement.

My observations, experiences and conclusions are very similar to Rick's after getting in and out of Sugar Bowl for the last 4 years with a long 2+ year layoff!  

1- No fatties for me either. I won't do them for free let alone pay for them. Fatties can be very charming and that's another reason I don't do long phone conversations so I don't get involved with the Fatty's mind games.

2- Those who have been "lucky" enough to have landed a sucker SD who paid them 5K+ per month (albeit perhaps only for one or two months max) and/or also got an auto out of that sucker SD, really need to have their balloons burst and I'm not interested in the least in them. If I had boundless amount of income, I would gladly pay 3K per month for one top notch SB who checks out to be a college grad at a good college, but I would not be throwing my hard earned $$$ after quasi hookers who just want to waste their allowance on BS luxury goods. Let them become full on hookers and then do whatever the fooque it is that they wish to waste their income on.

3- I have also heard that "I will make you very, very happy" BS statement. In the hookerland, it usually means CBJ only or a hand job using the cheap motel
s hand lotion in the seedy bathroom.

A- I agree to a certain extent but as SM pointed out, this type are more ready to go but if you want to date 'em and play the player game, the ones with younger kids are a waste of time in that regard.

B- same here although I am a few years older than you (low 50's here)

C- yes, same here but if the quasi pro is quite hot, in the 300 allowance range (in my market) and it's not just a wham-bam one and done type of ordeal, I will not shy away! If a full on pro who I recognize (including massage girls) I'm staying away.

D- 1000% percent. Lots of R.O.B types here too. Learned through unfortunate experiences on this type! No roof over head and no transportation (where one is really required like in So. Cal) means that they need 2-3 months worth of that meager allowance upfront!

E- I don't have those issues and I'm single and unattached.

F- I won't do married (with a live-in hubby) and if I find out that they have a BF, I may still take a pass depending on what my spidey senses signal to me.

G- Totally concur. I had also experienced this with the hookers who were not BSC and on drugs and other addictive vices

Pretty much the same thing as you on all those points. I have had one or two phone conversations, but that is not my preference.

I no longer walk away from a woman who says she wants 5k or more despite my budget being less than half of that, because in my experience for a lot of ladies that is just a starting point and the number drops quickly. Of course, the problem is that by starting there it puts me in a lousy position to negotiate a more workable number, even if she does come down by 50%.

I had been playing around with some responses to ladies who want 5k but admit to being newbies to this. At first I tried something about being just a bauble for a guy who can and does buy anything and everything, so he will likely soon move on to another new, shiny thing. Maybe I did not word it well, but it did not seem to fly. So now I say something more about finding someone you like, trust, enjoy hanging out with, and we will make the money work.

Since none of those have played out well, I am not convinced I am right to work that angle, but it is something I have been trying.

zig