OP: given you did post here for advice, I'm going to posit an observation. It may be that you won't like it or accept it. But it's not made in the spirit of goading; it's made from a genuine desire to help you drop those scales from your eyes. You posted here asking others what they would think to this message and your husband's subsequent behaviour. They're telling you. But over the last few pages, you've become very confrontational with PPs who have taken time out of their day to post answers: because I'm assuming they are not the answers you wanted to hear.
You discovered your husband's message. Your husband then turned this around against you - this is a classic abuser's tactic BTW, in case you weren't aware - to the point where he even emotionally blackmailed you about leaving the relationship. PPs read the same message and his response to you, and told you how inappropriate and unacceptable they would find such conduct. And now you're turning in anger back against them.
I'm suggesting to you that this anger, which both you and your D[?]H are directing against those who question that behaviour, is borne out of the knowledge on some level that those doing the questioning have this bang to rights. Another interesting factor is that there's a pattern emerging here. Don't you see what that is?
I can easily understand the perspective of anger against those doing the assuming about the sex workers. But your response to this seems not only incredibly naive, but a wilful blindness to unpalatable facts. Can you think of any other plausible explanation for those particular items being in his car? Not to mention the biggest red flag of all: a not insubstantial amount of cash. In a glovebox? How many transactions in today's cashless society require £300 cash payment, from the context of a car as opposed to the more usual wallet? Open those eyes, OP. Because if you can think of any other compelling reason, I'd be interested to hear it.
It's up to you what you do. I'm not joining the chorus of 'LTB!' because it's not going to affect my life one way of the other whether you stay with this poor excuse for a husband or not. It's your life. But ask yourself this question, OP. Why, exactly, have you posted here asking for help?