First post, trying to save my marriage.

So, my wife and I been together since high school. Had a kid young I was 17 when I became a dad and her 18. Now 20 years later I feel we are struggling. We have four special needs children, diagnosed with ASD and EDS. Our youngest is 4 he is non verbal ASD. My wife is chronically ill. She has EDS chronic fatigue syndrome. Reynard, pots and actually a lot more. She is a wonderful woman who only thinks of our kids and that in it’s self is a full time job. I work night full time some times over 50 hours a week, hell this week I am doing over 60. She is a stay home mom who handles 98% of the kids doctors and school appointments. She is always exhausted needs naps all the time. If she pushes herself to hard she has post external malaise, she gets that if she tries to pick up the floor. I am trying to be understanding and help and clean and cook and focus on kids when I am off work and before I go to work if they not in school. The reason why I posting this is I really need advice, tonight I was gonna write her a love letter/ cry for help. We have a DB or dead bedroom, last Saturday it was my bday and I wanted to spend time with my wife. We went to a movie at noon came home kids were having a melt down by 4 pm she was done for the night and I had to deal with the kids and help the over come what was wrong. We talked about my needs and hers and thought we made progress but while she wanted me to research and understand her and the kids issues she was gonna try and be more intimate with me with the understanding sex might not happen. Well I did research and I found great webinar for her and me to watch about girls with autism. Our 9 year old is so much my different then her brothers, when I brought it up to watch it together she said she said she does not have time, plus she has not attempted to be intimate at all. I have also done research her issues and tried talking to her about it but she seems annoyed when I try and talk and come up with ideas for us and her to make life better. So, back to the letter and advice I want to list things I want to improve in our marriage while also listening our past and the good times we have. I feel if me and her don’t make progress with each other we won’t last because I am feel unwanted, resentful and overwhelmed with work and kids and cleaning. I know she is always exhausted and is doing what she can but I need more I can’t do this with nothing. I need something to keep me going. Any advice on how I should go about it would be super appreciated. Sorry for the rambling I am doing this by txt and I hate/ suck at texting.