I'm am so very sorry to hear about your husband. I want you to know that I do understand, my husband was diagnosed with heart failure 2 years ago and age 55. Like your guy, he was used to working 10-12 hours per day and when he first got sick, he could hardly get from the bed to the chair. He was so very mad at everything and everyone. It is so hard for them to accept that there are things that they just can't do.
It sounds like you know that there are many different kinds of meds that can really help heart failure (if that is what it turns out to be - and it sounds like it is with the weight gain and not being able to lie flat to sleep). My husband is still pretty sick, but it is not due to heart failure - his failure is completely under control and is very stable. That means that he is very limited in what he is able to do, but he is able to do lots of things that bring him happiness. And one of his greatest joys is Rowdy!
If this does turn out to be heart failure, you MUST get him to a cardiologist that SPECIALIZES in heart failure - many cardiologists do not specialize in heart failure and it will make all the difference in the world to have a doctor that truly understands heart failure and is able to adjust his meds to fit his needs. The medication regimen for heart failure is NOT one size fits all. Meds that work for one person do not necessarily work for the next person. Some heart failure meds make you feel like crap - all these things can be adjusted, BUT it takes a doc with special knowlege of heart failure to be able to make the proper adjustments.
Another thing, because it is such a life changing diagnosis and people are usually very upset, mad, angry, etc - it is often VERY helpful for the doc to prescribe a small dose of antidepressants. My husband was very resistant to the thought that he might need a med for depression. He kept saying, "I'm not depressed", but the doc finally helped him to see that it might not be the classic depression, but the antidepressant could help him feel better about all the changes in his health that were making him feel angry and out of control. The antidepressant really helped and when things get very crazy for my husband, he will even ask the doc to up his dose till things calm down again. I NEVER thought I'd see that!
It is also very hard on us (you). It is such a helpless feeling to see your husband so sick and so unable to do all the things he is used to being able to do. You may have to do things for him that he cannot do and that will upset him and you. It is all very confusing and very difficult to manage at first. It does get better - you just have to take one day at a time.
If you need to talk - please pm me - I'll be happy to help you with anything - I'm also a nurse, so I know quite a bit about heart failure in general.
Good luck!