I can't speak to most of what you mentioned, but I can share my own experience re Medicare. I was already on Medicare when I was diagnosed in late March. Some years before, I had switched jobs, then went back to my earlier employer. I was gone only three months, but they wouldn't put me on the group health policy; they ordered me to go on Medicare. In retrospect, that was a great move. I chose traditional Medicare parts A and B, a drug plan part D, and a Medicare supplement. In my experience, I've received extraordinarily good coverage. I was hospitalized for three months in 2020 with myocarditis, likely caused by covid (although no positive covid diagnosis). Among other things, I had two open-heart surgeries, ECMO therapy for a week, a temporary pacemaker and then an ICD, multiple procedures on my left leg to fix damage from the ECMO tubing, and weeks in ICU and rehab. My total, undiscounted bill was $1.7 million. I know this because I had to obtain a copy of the bill in order to claim coverage on a hospitalization insurance policy through my employer. My total out-of-pocket charges were less than $100. This time, since my diagnosis in the spring, I've had six surgeries/procedures, a week in the hospital, and 14 chemo rounds, plus plenty of MD visits. I've paid nothing out of pocket since diagnosis. In both cases, I've never been denied care or required to get pre-approval to see a specialist. The healthcare system we use accepts Medicare patients. The drug plan part D is a little different because of the donut hole thing (which I think they're supposed to be fixing). I do pay a copay for meds. Most of the time it's very little, but I'm on Xarelto, and that one gets pricey.

I know that some people really like Medicare Advantage, but I will never go to an Advantage plan; the coverage with traditional Medicare and a supplement is superior. I know you said you have a few years to go, so of course you'll need to check the current coverage when you go to select a plan because things do change. I will say that our premiums are up there. Medicare comes out of our SS checks each month, so we never "see" that payment. On top of that, we pay for the supplement and drug plans. But to us, it's worth it not to have huge copays.

I'm glad others responded to the OP re disability coverage. I did short-term disability when I left work in the spring (I couldn't teach wearing the infusion pump--too dangerous to be around kids). I didn't seek LTD because Social Security was going to offset it to the point that I wouldn't have gotten any LTD payments, so it wasn't worth applying. I was already on Social Security; once you hit full retirement age, you can work as much as you wish and still get your full benefit. So SSDI wasn't an issue for me.

Mark,
Yes, I would think you could be on your wife's health insurance if she would go back to work. Currently my husband is working, and I am on his United Healthcare health insurance.
I was told - if neither me nor my husband (age 60) worked - we could apply for Obama Care, and the premium would be very low (if you have no income).
I was told Obama Care covers pre-existing conditions.
When it comes time to apply for Medicare, I was told to talk with SHIP (State Health Insurance Assistance Program)-it is a free program and they will help a person figure out what is the best plan-I was told to stay away from a Medicare Advantage plan.

Lots of good info has been posted by other members.

I am under 65 and on disability. Talking with the SHIPP counselors was one of the best things for me. I wish I had contacted them sooner. It would have saved me a lot of distress and anxiety. I had to talk with them multiple times and read the stuff they suggested in order to digest and fully understand all of the information. And I have a master's degree.

About the need for health insurance coverage after employment and before Medicare:
My employer had long term disability insurance, so my employer was able to continue my commercial health insurance for about 2 years (yes, two full years) while my Social Security Disability claim was being processed. Then, I paid for my same commercial insurance through COBRA. It wasn't cheap, but it provided continuity. After 5 months paying through COBRA, I was enrolled in Medicare since my disability claim was approved.
If you go from employer-paid to COBRA self-pay, you must do so quickly, within a limited time frame.
[It occurs to me that COBRA might be run by my state. Maybe your state government has a similar program with a different name. COBRA makes it possible for an employee to continue to purchase their exact same health insurance after they are no longer employed by the entity that provided their health insurance. It is not cheap. I live in Pennsylvania.]
I'm not sure if the following is relevant or not: When I called companies to ask about medicare supplement insurance, they all asked me if I had currently had health insurance. I wonder, if you go without insurance right before you qualify for medicare, then can the companies charge you more for their medicare supplement?
A SHIPP counselor could probably answer that.
When you first enroll in Medicare, be very, very careful about the secondary insurance that you select.
The SHIPP counselors, mentioned by another member here, really helped me. They told me to NOT get an "Advantage" plan. They said to use original medicare with a "Supplement" insurance, which are sometimes called "gap" plans, and a Part D plan for drugs. You give up a lot of control and a lot of options when you enroll in an Advantage plan. You have to stay within their network of doctors and facilities. This seems to be the same advice that the other member here got from their SHIP counselor.

My insurance costs are a hefty chunk of my monthly income, but it only takes the cost of my physical therapy sessions to break even. (I don't have cancer; I have a chronic disease.)

That's all I can think of to contribute, except my good wishes, so good wishes to you and any other readers, too!