Seems like you're facing some tough choices. You have a few choices:
1) Accept the company is going to shrink, and do so cleanly. Engineer the product to be maintainable by a small team. Acquihire away some of your engineers (although that's tough in the COVID19 job market). Etc.
2) Find a way to pursue major growth. This almost certainly requires you to do major pivots and take on major risks.
3) Do nothing, and watch the company go from black into the red. Have successive rounds of demoralizing layoffs, and watch the software bitrot into obscurity.
You can:
1) Continue to provide the existing product under the existing pricing model, with a much smaller market. You'll have less revenue, and less means to improve the product; you'll basically wait for Sidecar 2.0 to eliminate that vestigial market.
2) Continue with the product at a lower price point. I'd never buy your product for $80 / year, but I'd definitely do it for $5/year. I have an older iPad 2 I could repurpose as an additional monitor, or better yet, a digitizer tablet.
3) Go sleazeball and maximize short-term revenue: mine your user's private data, false advertising, the works.
4) Pivot into a changed world, and introduce something to add a lot of additional value. That requires vision, aggressive engineering, etc. Most such pivots fail, but some do work.
By far the biggest risk is to do nothing. That's a choice in itself.
Personally, if I were in your shoes, I'd think through remote work and remote teaching right now, and see how to best support that. That's the growth model. iPads have digitizers, spare cameras, etc. all of which can be awesome for this sort of work. So do many other devices. Cross-marketing can be huge here too (cheap software, expensive hardware up-sells, or expensive integrations). You can often make more money as part of a solution in an ecosystem than as a solution.
Best of luck.