You said it yourself... the sex is getting boring and she is obviously starting to get on your nerves.  

On to the next one.

Once the sex gets boring, time to move on.

When the sex gets boring with an SB it's well past time to move on.

Not to mention that over-ordering shit won't fly with me for a second. I don't really mind being the guy fucking some college kid's GF because he can't or won't step up and treat her right, but I refuse to be "that guy" the one slobbering all over her, giving her gifts, money etc just so she can run home to him and share the food that I bought her.

I remember a friend of mine many years ago was raving about the "chemistry" he had with this hooker/SB he was seeing. She also happened to work for an agency who's owner was a friend of mine. One week he was raving about her yet again and told me he had "treated her" to a couple of grand so she could go visit her mother in Miami, and that he didn't mind even though it meant he wouldn't be able to see her that weekend. Little known to him, she was taking HIS money and taking her "real BF" to the beach that weekend, I never had the heart to tell him the truth. but I resolved to NEVER be "that guy"

You don't necessarily have to bail, but you do have to act to take back control.  

Personally, I don't care what she does with her money. And it is HERS, not yours, once you hand it over.  It took me a while to get my head screwed on about this. I used to get bent out of shape if she spent my cash on frivolous things, let alone another guy!  But remember that her inability to save or spend wisely is a primary driver of why she wants to suck your dick.  

Now the demands for more sessions per week and ordering extra food are a different issue.  You need to control this behavior by changing yours.  If she wants to go from 2x to 3x, don't be available.  In fact just be available once a week, or event once a month for a while.  If she asks for more time, tell her you're slammed at work, have family visiting from out of state, or whatever sounds good.  In fact, the more lame your excuse the faster she well see that you are deliberately walking back your interest.  

As for the meals, discover Denny's for a while, telling her you just want to grab a quick bite and get home (or to the hotel) to really focus your time on her fun! Better yet, grab a Taco Bell burrito before you meet and blow off the meal altogether.  

After a while, she will either bring her expectations back in line to the original arrangement or she will bail on you (and start banging an SD with a bigger wallet and less self-respect). Either way you win.  

-The Cat

No need to discuss, just go silent or tell her that you have money issues right now, if she still continues seeing you which I doubt then you got your renegotiation done without a discussion. Most probably if sex is not good then why burn the cash, just move on to the next one. That is what they do whenever they feel like.

Familiarity does breed contempt.

Once the sex gets old or boring there's really hardly any point in trying to salvage the situation.  I've had several one time hookups with SBs that were simply not very good, so I moved on right away and did not see them again.  But if it starts out good and then deteriorates, cut your losses and move on.  

It's a two way street. You should bring new things on the table and explore together. Toys, threesomes sex workshops etc etc. it will add spice to sex.