You should continue tighter vs a cold 4bettor than if the initial raiser 4bets you. The cold 4bettor has two uncapped and strong ranges that he's reraising. Not only will you defend vs his 4bet but so will everyone left with cards. Because of this you can play tighter without worrying about being exploited. How much tighter and what range you should use vs the cold 4bet is a much harder question to answer.

Also your defense should be split up between calls and 5bets. You're getting an excellent price to call so surely there are some hands in your range that will work better as a call instead of a 5bet.

The defense vs this 4bet should be 41% in order to prevent cold4bettor to 4bet any two cards.

19.5 / 19.5 + 13.5 = 0.59

1-a= 0.41

This 41% is divided among BB (will continue only with KK+), OR and 3bettor basically, OR is forced to drop all bluffs as he has the 3bettor behind uncapped, so assuming he continues with QQ+, AK (he is on HJ), and can't really flat a ton with me behind. That is 2.56% so about 10% of his OR, adding some flats can reach a max of 5% (TT+, AJs+, AQ+) which I consider almost noone defends. so that would be 20% leaving us with another 20% to defend as 3bettors.

If I defend only my value 3b/5b and drop my 5b bluffs I would be defending 2.56% from my 10.7% 3bet on this spot. I would be defending 24% only by myself.

So realisitically, OR will be defending 10% of his OR and leave us with 30% to defend.

I have 34 value combos (QQ, AK) and 10 bluff combos(3b/5b) for a total of 3.32% range -> 31% defense.

Also my 5bet bluffs have 30 %equity vs cold 4bettor strong range (QQ, AK), and gain also from cold4bet bluffs that folds.

So, should I defend 30% or less and let OR defend more than 10%?

Agree with Doncamatic here. Since you're against a cold 4bettor, I wouldnt worry too much about him 4betting any 2 cards and exploiting you. And you're getting 3 to 1 on a call, which should incline you to flat with some % of your range and play IP.