TAMF,
I am so sorry that you have found yourself here. Not everybody going through this make it here. So now you get to read.
These people here will help you and know what they are talking about. It takes a while for all of this stuff to sink in. Even then there will be times of doubt that you will have to conquer.
This was a trip that you did not start. That part is huge to get to realize about this wacky mess that will keep unfolding. This
Monster takes time. Lots of time. You will get the help you need if you ask for it. Many have been through most of what you described. I love the "you two had the perfect marriage" in your post. Remember this: If people said that to both of you throughout your marriage, then it was probably true. I have been there and done that.
Now.... you have people here that really understand this journey that you will take as a LBS. Some stuff is going to hurt but you will grow in ways you will not see. But others around you will see it.
They will tell you when you do. You won't necessarily see it in yourself, but if you do the work that you must do, it will payoff in the long run. I do mean loooong run. It takes time for you to get used to this. It is like learning a new instrument or procedure for the first time and you know how frustrating that will be. That is when you truly have to dig deep for patience.
Patience is going to be the #1 weapon to protect you. It sounds like you already have had an OMG moment when you stated I have come to realize that my H is in a full blown MLC. You will make mistakes, maybe many mistakes, but the lessons learned will be very valuable. Hang in there, it seems like you have got a great start!!