AAxx how to proceed w/no sidepot?

Live 2/2 9 handed no bring in. Timed rake.

We just sat down not too long ago.

1 limper in utg
Hero in +1 opens to 10 w/A♥A♣8♠J♠

Mp 3bets to 35

Btn coldcalls(effective 172)~ he min3bets every single hand.

Hero asks mp how much effective.
We thought mp only playing with 200ish, we repotted to 155.
Turns out mp had 2 blacks hiding (So actually around 450 effective).

Mp calls
Btn ships for 172
we both call.

3way main pot 521 sidepot 0
Flop K♥J♥8♣
We supposed to jam right, mp only has 300 left.
If we only had naked AA do we still jam no sidepot?

Hero was supposed to flat the 3bet if we knew mp had 450+ effective? Or 4betting is standard even w/aa trash?