i would likely raise flop, villain seems fishy and will have tons of pair +fd type hands that will bet/call. i really want to charge villain to draw to
's.
i would find a raise on either flop or turn, and river is easy fold
I would almost always raise the flop against any opponent. At NL25 you can just raise as a default unless you have a good reason not to. Regarding sizing, 4 is good.