Self respect and happiness are definitely important, and mostly, do come from within In order for you to live your life with the values you hold dear, that may include not putting up with certain behaviour though, and only you will be able to figure out whether that line has already been crossed too far or not. Hugs to you in your position, It's not a nice place to be
Just my opinions here from things I have learned: I think if someone is going to stay after one person has cheated, it needs to be a big decision. Because the cheater needs to understand that it will take a lot of time and effort for the other person to trust them again and the other person has to wholeheartedly want to work on the relationship too. If the cheater thinks they won't be able to put in the effort to gain trust again (and they truly need to be honest with themselves here) or the cheated on thinks they won't be able to avoid throwing the cheating in the other ones face during every argument, it's just not going to work.
I don't think you wanting to make your DH happy is a bad thing (I do lots of things to make my DH happy) but it needs to be a two way street. Both parties need to be able to have the utmost respect for each other and genuinely want to do things to make each other happy, because you love each other, not because you're hoping by acting a certain way it will prevent him from cheating.
I think the biggest difference between my ex Husband and my DH is selfishness. My ex was a very selfish man, right through the 14 years we were together. My DH is extremely unselfish, which is what gives him his, as you put it, 'pure' personality. He would rather go without himself than see me go without, be hurt or upset.
So I guess it all depends on personalities and why they felt they needed to cheat in the first place and IMO, if they are not willing to take the blame for the way they have acted and handled the situation, if they try to place the blame on you, there may be little hope. (Even if a relationship was failing, they need to be able to admit cheating was a disastrous way to handle it).
When I left my ex Husband I did some extremely helpful little courses through Relationships Australia. I am pretty sure they have some for couples wanting to overcome infidelity or broken trust. I'm not sure if you'd be interested, but I found their courses really helpful