My answers to some of your questions:
Should you write a review?:
Normally, I suggest that newbies not submit reviews until they have seen at least a few different providers. I advocate this mainly as a way to garner a few data points before trying to rate experiences.
However, in this particular case, I can see the merit in submitting a review mainly - as Crystal pointed out - as a heads-up to other potential clients. Frankly, some guys don't mind this kind of encounter, but a guy looking for GFE should certainly move on to another provider.
In the review, mentioning you are a newbie and also noting any circumstances that were beyond the lady's control (such as the Celexa) would help to temper the negative aspects of your appraisal. You appear to be relatively thoughtful and can write a coherent sentence, so I think you'll manage to write a fair review that won't provoke a "flame-war".
What to do about the differing rates on different ads?:
I have experienced this before when contacting a provider. I simply said something like, "Is the hourly rate that is shown in your ad on [Eros] your current rate?" Never had a problem with that approach. Also, I almost never go by the rate shown on her TER profile as that is rarely updated generally.
How do you handle the tipping?:
If I feel like the provider exceeded my expectations in one way or another, I will leave a tip at the end of the session. As Bostonguy pointed out, no need to be too circumspect about it. The provider should have figured out by this point that you are not LE. Besides, I hear that vice cops are notoriously cheap, so they wouldn't be leaving a tip anyway 
What to do about the TV?:
I don't have a TV either, so I can understand how completely distracting this can be. Horrible for the mood. I have encountered this three times. First two times I didn't ask her to turn it off. I was new and she was in control. Never again.
Last time, I asked to turn it off and she said she might make enough noise to warrant some background cover. She did, however, change it to a music channel at least. Fox News just isn't gonna work for me.
What to do about the early end to the time?:
If a provider is making subtle (or not so subtle) signs to encourage you to get packing, you could politely ask if you could simply chill, or cuddle, or talk, or whatever for a bit until your [hour] [90 minutes] is up. This, of course is assuming that you were enjoying her company in the first place!
I did this with one provider and she replied, "That would be great. I just wasn't sure because some guys simply want to come and go." We spent a very nice 15 minutes laying next to each other, talking and laughing.
Is the provider's age an indicator of her tendencies?:
No. Not necessarily. Of my two favorite providers one was 23 when I met her, the other was 33. This is not to deny that there can be general trends (ie. youth = immaturity), but it is very case-dependent. For example, take a look at Brooke Song's profile on here. She is young (18 - 20) but ... well just look at her numbers. Based on her profile and her board posts - back when she participated more - I would say she is more mature than 90 percent of the population.
Good luck. Be safe. Have fun. Treat the ladies well.