5-10 plo hand

pretty loose game. utg a wild player limps. he limps with any 4 cards. player to his left calls. he's totally new to the table. im to his left in middle and call w/kka3 rainbow.
all fold to blinds who call. flop is 999, blinds check,maniac checks, new player pots it, i call (im either a huge fav. or a huge dog here, no reason to raise or fold right?)blinds fold, maniac calls.

turn is a 5. maniac checks, new guy checks, i figure im a huge fav. at this point and decide to bet for value. i figure $50 will get called in at least 1 spot. i bet $50 both call, nice.

river is a 3. maniac bets out $10 he has done this for years it means he has a weak hand. it is a 100% tell. now the new guy springs to life and bets $150. What's your play?

results to follow.

I call. if youre reads are correct utg is not a threat and new guys play is consistent with QQ or JJ or a bluff but is not consistent with quads or AA. that being said you were probably shown the 4th 8, otherwise you wouldnt have posted. see as a poker player im always trying to read something into everything.

well...i called on the riv. the dude turned over 6789 for quads. was there any way to avoid this call. not knowing anything abvout the guy he didnt play like quads with the pot bet on the flop.