I am by no means an expert, but I did just go through the whole buying process so since no one else has said anything I'll give my two cents.
You're going to have to test ride the bike at some point. I know that being in a city makes that kind of inconvenient, but the bike store probably has a specific route they've found is fairly safe and a good test of the bike for you. We live in Boise but ended up buying our bikes in San Francisco. There were bike lanes and a route that suggested that wasn't totally traffic-y and had some hills to try. I would just ask the bike stores you are looking at.
Most bike fitters I know of are definitely associated with a bike store. I'm sure there are some independent ones, but most stores just hire a fitter kind of as a contractor. The Specialized dealer here has a whole separate studio just for fitting. Like you pointed out though, they fit you, and then recommend bikes from the brands they carry.
Most reputable bike stores should have at least a couple knowledgeable employees who by looking at you, and finding out about what you want in a bike, can narrow you down to a couple of bikes...which you then would need to test to rule some out.
I probably test rode 8-10 different bikes at a few different stores before I decided. That's just kind of how you tell. Even though there were bikes the stores swore up and down I would love, I didn't necessarily. It's all about the feel. A much worse option would be having them put the different bikes on a trainer to see how they feel, but obviously that is in no way similar to a ride.
If it's an option, maybe go out of the city and find some bike stores that carry the brands you're looking at. You can ride them there on less crowded roads, get a feel for them, and then buy at your LBS.
As to your last question, that information is usually on the manufacturer's website, not sure what bikes you're looking at or why you're having a problem finding it. If nothing else, the bike store can hang the bike on a scale and find out for you.
In summary of my comments above, I personally wouldn't waste my money on a fitter, because you're going to have to test ride the different bike brands anyway.