Q1: Villain plays perfect and so should we, if we don't and decide to overfold we give him EV.
Q2: Yes we gain EV because we win more often when we do bluffcatch

Okay. I did some work in PIOSolver to come up with a solution to these questions and want to see what you guys think. For this example, I used a SB 3bet vs BTN raise and Btn call. Flop Jh 9s 6s, Turn 2c, river 3d.

Question #1: I kept OOP river betting strategy the same and only changed IP's calling strategy. I got rid of some of IP's bluff catching hands that were very close to 0 EV and recalculated the EV of both players. The EV of both players stayed about the same. When IP got rid of some of its bluff catchers that were virtually indifferent (like A5s, ATs, AQs, 64s, and 53s), OOP's EV with his value hands decreased slightly and the EV of his bluffs increased slightly, but kept his overall EV close to the same. But if I take better bluff catchers that aren't aren't close to indifferent to calling (like some of IP's 9x hands), you significantly increased OOP's EV. That's because these hands AREN'T indifferent to calling.

Question #2:
I used the same above example, but gave OOP more bluffing hands and kept IP's call frequency the same. At equilibrium, the EV of OOP was 1190 and IP was 242.71 when IP is facing a bet from OOP. But when you give OOP more bluffing hands, it changed to 997.12 for OOP and 435.89 for IP. This is because every bluff catcher in IP's distribution increased in EV, increasing the overall EV of IP.

Conclusion: My conclusion from this is if a hand is truly pretty indifferent between calling and folding, you should probably just fold and lower variance because you don't really increase the EV of your overall strategy. But if it is close and it is possible for your opponent to be bluffing too much, then you have situation A where your EV of calling is pretty close to 0 and situation B, where your opponents bluffing frequency is too much and your EV is decently positive. If you average the two scenarios, then you are incentived to call. But the reverse is also true. If your pretty close to indifferent, but slightly +EV to call, but you suspect your opponent might be underbluffing, and the EV of your call would be negative, then your incentived to fold. This is my take on it. What do you guys think?