Id call river , id probably raise turn as'well people wont come back over the top on these type boards without the nuts especially deeper, but i want to charge certain hands like sets and KJ , river usually checks to you so it plays easy.

Many might think it's nitty but I agree you're usually calling here to split at best. Like you say it's normally to stop you checking behind.

When he leads into two players he's not bluffing. I expect him to have Qx+pair at worst. I'd also expect him to check sets and two pair once the 4 straight appears on the turn.