GrizzledYeti, congratulations on your new dog!
Your room should be just fine, and Ysobel will probably be more comfortable in it than a more confined kennel. Remember it is your room, where you let her eat and sleep, not her own territory. It is no different from a kennel for a smaller dog, where the owner should be able to put their arm in without worrying their dog will resist the intrusion. Any sign of territoriality against you, don't tolerate it.
Sit and lay down can be very difficult to teach Pyrs - partly because it is in their nature to spend their working hours standing, partly because they are designed to think more for themselves, and need and accept less direction from people. Any time she does it on her own, you can say the word sit or lay down instead of click or yes, then follow up with a treat or attention reward. You will have easier success with "place" to keep her at a respectable distance while you eat, I would not worry about whether she is standing up while you eat.
Another thing you may want to work on is getting Ysobel used to you touching and poking her absolutely everywhere. This means lifting her lips to look at her teeth, putting your hand around her muzzle and applying gentle pressure, looking in her ears, picking up her feet and playing with her toes, giving a massage, etc. If she shows any resistance, stop and work slowly on that body part until she relaxes again. Because she has lived on the street, she is under the impression that everyone is competition. Her food aggression towards you is a trust issue, and this will help you as you work through that.
Don't worry too much about the walks, just make them slower and shorter than what you would like to progress to i order to give her adequate exercise once she's healed.