I know what a revocable living trust is, and I know what a living will is, but I've never heard of a revocable living will trust.

You don't have to file when income is too low, but the understaffed IRS might come after you if you applied for an EIN and never filed. Maybe, but not definitely.

This is not your issue, but if an estate or trust has capital sales, like stocks or mutual finds, and the sales proceeds exceed the $600/$100 exemption, I want to file to have it on record that any gain was low or a loss was incurred.