I really don't know about the price. The only meaningful way to judge a price is to get a few different estimates for the exact same work and compare them. The work he proposed seems reasonable. FYI you could do it yourself - they rent the machines to blow the stuff in, pretty simple - make sure the "vent keepers" or Styrovents go all the way to the vented area of the soffit.
I would never dump heat into a crawl space - it just doesn't make sense. I still say that you could probably dig out the crawl a little to be able to get in there or slide rigid sheets in there like I mentioned in previous post.
Your previous questions: Any hardware store will have these foam thingys the size of your switch or outlet covers that go behind the covers to seal any air gaps. Gas vs. Wood = there is no right answer really. It depends on different things. I got a wood insert because I have a wood stove in another part of the house, so I already have a wood supply and I like wood fires better. Many people like gas b/c they can just start and turn off, etc. whenever they like and no mess or smoke, etc. You have no reason to go ventless though, especially since you have a chimney and you are using it for heating and not only for decoration. French door = you need (at least) a new sweep or bottom of door weather stripping device installed to stop air infiltration. Also, weather stripping on door shouldn't let in any air.
Some combination of things will improve your situation. I can't tell from here what they are. Basically, keeping any area comfortable is some mix of; A. Adding heat to the area; B. Insulating to slow heat loss; C. Minimizing air infiltration. You can keep an uninsulated space comfortable if you throw enough heat into it - not smart or cheap but it can be done. You can super insulate and seal a room to minimize the amount of heat needed but you quickly turn this into overkill and get diminishing returns after you do the basics. I would do what you can to insulate, including rigid sheets slid under floor, investigate the heat supply for this room and maybe consider simple zoning, if appropriate, and consider adding more heat supply to it, maybe a duct booster fan could solve the whole issue, don't throw heat into the crawl, and maybe add supplimental heat as a stove or insert. Some combination of these factors will end up working.