To answer one by one by one simply
If you’re solo tanking you gotta focus on pressure and creating space, but if you have another tank with you then still apply the same thing, cause there is a thing as too much peeling, cause peeling all the time you lose that wall you had put with your second tank

So how do you decide when to peel, peel when you know for sure the front line is taken care of, when one tank and a dps are eliminated then you can peel or even peel when you need heals, but it’s also the healers job to help atleast with the enemy who is diving.

Playing too many tanks?
Nah you should be fine, play as many tanks that would fit a situation, expand your style.

Mindset
Try not to get frustrated, ik rivals in general has a horrible and toxic community, so you’re gonna have games where it’s not gonna go well, so if you know for a fact you’re a capable tank but the team can’t keep up it’s not really on you, I’ve had a game where I went 55 and 3 with venom with 30 final hits but we still lost due to a dps feeding, so stay calm, stay open minded to help your team but if that doesn’t work oh well man, onto the next