Yes it certainly wouldn't do her any harm to have her back checked but i wouldn't worry too much about her back if she isn't showing signs of lameness or soreness: if she starts reacting to being ridden then i would deffinately have her back checked.
With regards to your weight, i know plenty...
Perhaps it is worth while advertising your pony again and like already stated, make sure you use contracts and visit your pony regularly and vet the home before she goes. It might also be worth seeing if any local riding schools would have her on loan while you are at uni. At least then you will...
Personally i would have the mare as a sweet nature is half the battle when retraining any horse.
I would give her a month or so off to wind down and be a horse for a while. then start hacking and small amounts of schooling in walk so that she can build up muscle and strength in order to cope...
I think it depends entirely on the student, the horse and the instructor.
I have had lessons from a Pre St George dressage rider and found her useless! My old gelding learnt best in lessons that were short bursts of good experiences in the school rather than 50minute lessons of 'pushing him'...
The top producer that i work for always blackens the hooves.
Personally, i think that if your horse has more black than white on its hooves then blacken them. if its more white then paint them clear. once you have been to a couple of shows, you should be able to figure out what other's do and...
Personally, i would avoid doing anything smaller than a 20m circle, because his muscles will not be developed enough or strong enough to cope with it for any benefit.
I know how frustrating it must be to want to get on him and test what he might be able to do now compared with how he was...
I have been involved in the rehabilitation of many ex race horses and often saw the same problems you are having at the moment, where they have been used to simply gallop flat out in a straight line and often become stiff and unable to bend.
The physio should be able to work out the muscles...