if you start training and eventually get better, go for fly half! eye co-ordination is needed to visualise gaps in the defence and call moves and a good hand is great for the passing and finishing. Get better at tackling and also when you go running you'll get quicker! this postion is perfect for you trust me.
prop hooker or number 8 i think, in hooker you need to throw lineouts so it's pretty specialised
if you're new to the sport anywhere in the front row can't hurt probably prop as its a less specialised position and easier to start with (you won't have to worry about technique of hooking and taking line outs).
I would say hooker, but if youve never played before just go to your local club because youll need to learn the game like basic tackling and passing, rucks a mauls and im sure the due to your ability the club will know the best position.
try hooker or prop