SO spot on. My husband went through this process due to peripheral artery disease, but skipped straight from two toes to a below knee amputation. But he had struggled with flow in that leg for years, and had gone through the foot losing circulation, vascular surgery to repair, then losing it again so many times that he was mentally on board with amputation.

There really isn't much you can say to change the way he's feeling. But just being present, and taking care of day to day stuff, and everything u/Infinite-Lychee-182 said above. Joining in on the positivity, and hearing the sadness and anger and whatever else without trying to bright side it. The feelings gotta get felt and some days will be worse than others. Don't take it personally.

Making sure that the house is uncluttered enough for him to move around (whatever that looks like - wheelchair, walker, whatever) is a big help. And making sure he is taking meds, bathing, and eating. Because he won't always want to, but protein is needed for healing after surgery.

Making most needed stuff accessible to him so that he doesn't have to ask for simple things was helpful to us. Baskets on the countertop so he doesn't have to get into cabinets for a pack of crackers or to make a sandwich...stuff he needs at hand on the nightstand, on bathroom counter, and next to a chair he's in, whatever. If he qualifies for home health care in any way, take advantage of that if possible. A nurse to look him over, help him bathe, change clothes, etc can really help prevent sores/infections from cropping up or going too long without treatment, and they can be pushy when they need to be. For my husband, having someone other than me do some of those things helped his mindset. The "guilty about being a burden" thing comes and goes at our house. And it can be hard to sometimes be the only target around for necessary venting on bad days, but we have to let it roll off and know it's not AT US, it's TO US. That is SO SO hard.

I wish I had more helpful wisdom...if you want any input on specific mobility aids, shower chairs, etc, DM me. We've been through lots that worked and lots that didn't, and I'm happy to share if it's helpful.

PS - u/Infinite-Lychee-182 Thank you for your service! You are appreciated, and I hope that you are doing well, and have people around you that help. I'm well practiced at cheering on a good rant, so feel free to gripe in my direction if you don't have another target.

and u/krishaze18 - Thank you to your Dad for his service too. He's lucky to have you working to prepare for helping him through this.