I think history might be a useful guide here, since Trump himself has no concrete ideas and simply operates off of general feelings about things.
Back in 2016, one of the things Trump ran on was the idea of repealing and replacing Obamacare. It was a pretty common talking point.
After Republicans gained control of both the house and Senate and Trump won the presidency, they finally unveiled and voted on their Obamacare replacement plan.
If you read through the text of their new plan, it was essentially an Obamacare lite plan. A lot of the same basic protections still existed, but the subsidies for healthcare premiums were reduced significantly and tapered off rapidly for middle / high income folks. IIRC I remember reading their new subsidy formulas and thinking "well, if I keep my income low enough, I will still be fine"
In addition try also tried to implement Medicaid work requirements in several states.
None of this really came to pass - except maybe some of the work requirements, but I think even those were struck down in the courts.
I suspect, since Trump did not even run on repealing the ACA this time, that mostly they will just make some changes around the edges. Try to reduce subsidies, remove women's healthcare, try and add work requirements, remove funding for advertising, make signing up harder, etc.
Who knows how much of this will come to pass, but I think at this point even the Republicans realize there would be too much chaos in the healthcare markets if they outright repeal the ACA. So I personally don't see this occuring, but I also recognize that I might be eating those words this time next year.
No matter what, we will probably know within the next 2 years, and probably within the first year of Trump's presidency, what their general plans are for the aca. I imagine this is the sort of thing they would want to make any changes they are going to make while they have control over congress, so can't risk waiting too long.
I don't know anything about politics though, so I could be horribly wrong about everything.
ETA: In terms of backup plans, my backup plan would be to get a part time job somewhere for benefits, or ask my spouse to get a part time job somewhere for benefits.