Home: help with a hand

[Plaxus]

Single table home tournament. 7 players left, top 3 pay.
1 player with about 4K chips, rest of table fairly even around 1500. Table is playing fairly tightly. Most pots are staying pretty small and are being taken down by modest bets.

Blinds 50/100
Folded to SB (1500 chips) read: fairly straightforward, Loose Passive.
SB completes 100.
Hero in BB with 1400 chips (Ah 6s)
BB checks.

Flop:
4c 6c 8s

SB bet 125.
BB raise to 385. SB calls.

Turn: Ad
SB checks.
BB bet 400. SB calls.

River: 5s
SB goes all in.
BB ??

Will post results later. How is the play on all streets? Does the pot size and nature of my hand warrant an allin on the turn? Do I fold to the bet on the flop? Your thoughts?