starting OD is too low for SF - at 6'5", unless you do 1-position training, it is going to take a long time to get it to at least prolific. I tried 2-position Level 4 trainer a while ago on a 6'7" and the pops took much longer than shorter players. The good news is for you if you do decide to go down this road is that your ID will pop as well while you train pressure and his height will somewhat help.
atrocious passing is also another difficult one. I like passing so this is a major issue, but only to me, not to everyone.
for me, the atrocious stamina and free throw are the final reasons I would urge you to consider selling him while he is 18 and the price is high - you are going to potentially lose a lot of games while training him because of stamina and FT - maybe not in Div 5, but most likely so if you move to D4 and D3.
Not the most happy comments, but it is only a suggestion. If you decide to train, good luck and may the training gods smile on you.