^^^^ What WhoIsThis said.

There is actually a way to do it with 137, but it is a pain in the booty because it required some crazy loadouts. Elly's guide works like a champ. You will need to buy a pink lvl 43-45 strength booster set (Osiris gear, usually).

Your spell damage will be affected. Not horribly, but I will tell you that Heal takes a big hit. I don't have the numbers in front of me however. You are correct that weapons affect spell damage, but Int feeds into them even more. So although you will "gain" some with the Str weapons, you will "lose" some spell damage because you are putting 138+ into Str.