There are some similarities to our situation and we decided to declare assets and have a joint sponsor. I am the Beneficiary, and work for a company that is 100% remote working so I could prove my income would continue. My wife (USC Petitioner) has been a Hausfrau these last 6 years and has not submitted a tax return because she has had no income.
What we did was file the latest 1040 and include a copy. Use my income and our combined assets, which put us over the top. However, I had read that approval of I-864s depending on Beneficiary income and assets is down to the discretion of the Consular Officer, so we included a joint sponsor too. We wanted to have backups to the backups.
For me, use everything you can to get you over the 125% benchmark so that there can be no question it should be approved.