Hi there. Sounds like you are the support he will need. My wife was the same for me. I would not have made it to the hospital that night without her.
I had a dissection and aneurysm and drs replaced the asc aorta and other bits in OHS.
Search for my first posts to this forum about 1+ year ago. I have a list of recovery tips.
The most important (for me) was to practice lying on my back when sleeping. If your husband can do it now start sleeping on his back only. After surgery he MUST sleep on his back for at least six weeks to let that sternum heal. And it took me about six weeks to get used to it and it wasn't nice at all. I was an emergency surgery so no time to practice, and no idea what I was in for. I went for 3 months on my back and now it is hard for me to do otherwise. But it is a good thing.
So that first six weeks is going to be the most important to get that sternum right.
Therefore, no reaching, no stretching, no bending over, no tying shoes, no crouching, no physical twisting or flexing. They told me about the cylinder, keeping within an invisible cylindricalbarrier, tucking elbows gently in, and not extending out arms for any reason.
I needed assistance for showering, dressing, getting into and out of bed, going to the bathroom (esp number two) and wiping. I found it easier to have shower after the number two than to try too hard to reach around.
(sorry everyone for the descriptions - but we are all here for a reason)
If your bath is also a stand-in shower then getting into and out of will be difficult. Try to avoid slipping. Really try. A slip can tear wounds and break fragile mends.
Wear slip-on, safe shoes. Open shirts that button easily - there will be NO over-the-head method of wearing shirts. Same with pyjamas.
The sternotomy wound will be super-sensitive - give it some space. For me the slightest touch meant excruciating pain and discomfort. (back sleeping to the rescue!)
Walk.
He will need to walk even though he won't like it.
I forgot how to walk. I was in ICU 5 days and in the ward I couldn't walk. My body was ruined and exhausted from the surgery and recovery. Nine hours or more for my OHS.
Walk outside on nice flat ground, grass or pavement. The legs are the powerhouse of the body. They will pump the blood and keep things in sync. Don't push too much, don't struggle, and stop every few yards - strength will return after a time. I used to go to the mall and walk up and down past all the stores. Kept my mind active so I would forget how boring walking is. Make sure there is plenty of supports.
Get out of the bed, and out of the chair. He is not going to re-learn how his body should move if he is lying in bed. But he should pace hmself, and not go too hard.
Focus on good foods, and some meds will make everything taste like cardboard. But eat like you're sick (because you are) and get the best nutritious foods. That heart has to heal and the wounds have to mend. Give the heart and aorta so much love and support.
Check yourself (and when I say "you" I mean "him" because this is general advice for all "you"). Check for symptoms and signs. If you are doing to much - stop. Your body will tell you when it is hurting and you have had enough. If things change esp chest and heart, seek medical help.
Check urine and poop for any signs of blood (internal bleeding) - if found, seek help.
Take meds - always. Never skip a day for any reason - you can quibble with doctors later but for a start take your meds. If you have missed a dose, don't double dose or "catch up". Just take the dose later that night or when you remember and resume dosage next time and listen to pharmacist or doctor advice - that will be a question to ask before discharge from hospital. What if I miss a dose?
Get into a rehab program - think about it now. I don't think I live near you so I cannot help here. But there should be at least one hospital offering cardiac rehab. Don't skip the education component, and attend with him so you can learn something.
Ask questions. Always ask questions. Information is a powerful tool for recovery. PM me if you need. My CT angio scan is on 11th. I will thinking about your stories.
Tell us all how you are doing.

(edit: I just realized how long that comment is - sorry, but I hope it helps)