#3
I definitely wouldn't spend any more than that on a replacement neck for a $110 Strat. Just remember that you get what you pay for. A $37 guitar neck is liable to have its issues.
#4
kinda doubt that neck would be any better than what you already have. save your money and get a better guitar.
#5
Cheap guitar + cheap replacement neck = still a cheap guitar.

Probably not worth it. Buying cheap means buying twice.