Dear Mum of many~
25 years is a long time and people change and one of the changes is they can become mentally ill, maybe depression, maybe anxiety, maybe something else. Not being able to keep a job, failing under pressure, not communicating, all point in this direction.
The very best thing you can do for both of you is encourage him to seek medical support. See his GP, set out all that is happening and how he feels. See what happens next. If he has an illness, which sounds very likely, then he will get treatment, maybe medications, perhaps therapy. Most such illnesses respond well and the person concerned very often leads a pretty normal life.
One hassle right at the start is some do not accept they need help, then it can be difficult to persuade them to seek it out. You may be able to succeed here, or perhaps enlist the help of someone he will take notice of.
Feeling he does not take notice and reacting with hurt and anger is natural, however normal judgment may not apply, if he is depressed he may not be capable of more. This is another reason why he needs diagnosis and medical support - so you know where you are.
It is a very difficult time for you, uncertainty about the relationship and the future, uncertainty as to what to do. Do you have anyone there for you -a parent or family member or friend? Being able to talk frankly how you feel, get ideas and support all make a pretty big difference. You are under a big load.
You can talk here