First you should fold less than 67% vs a 3b if you don't want to let vilain immediately profit from his 3b.

That being said, knowing what a pseudo GTO is should only be a tool for exploiting people in a sense that it gives you à good idea of what frequences and ranges should be.

Say that GTO tells you that it is correct to fold between 40 to 50% to cbet, if your opposent folds 60% you know hé is over folding hence you shouldn't be affraid to add bluff to your theorical cbeting range (and tightening your value range as well).

It seems like you want to maximize your EV. GTO does not do that for you. If you want to maximally exploit your opponent's tendencies and leaks you have to deviate from GTO. GTO will only earn you more EV than any other strategy if your opponent is also playing perfect GTO (nemesis). In any other case, there is a strategy that is more profitably than GTO. The only problem is that when you deviate from GTO you become exploitable yourself, but if your opponents are not trying to exploit you (or dont know how or dont even know what exploitation is) there is no reason to try to play GTO. Just exploiting villains will be better for you. In your example, if villain is 3-betting tight and for value only, there is no reason to try to play GTO against him. Just fold always to 3-bets from him until you realize he added bluffs to his range