Few points to consider:
1. Twitter's current user-facing feature set does not require a large cash burning work force or infrastructure to sustain. There is plenty of room for waste reduction and cost savings, even after the current lay-offs.
2. In fact, current Twitter user-facing feature set can be sustained at such a low budget that, Elon could fund it out of his own pocket indefinitely WITHOUT any major TSLA sell-off.
3. Caveat: Initial capital infusion is required for implementing some new back-end features that will enable sustaining current user-facing features on a much smaller budget. Eg: automated spam filters, bot filters, new monetization features, etc. After that, it can run on a low budget.
4. Any new user-facing features that Elon wants to introduce can be monetized appropriately. Eg: Financial transactions with a transaction fee, video clips with ads.
5. Ad boycott is just temporary drama. There are PLENTY of supposedly bad platforms that find enough advertising dollars because they have eyeballs. If the users are there, the ads will come.
6. Elon's focus should be on ensuring users stay engaged. Drama and negativity is not necessarily a user repellant. At times, it can actually attract more users. Trump brought a lot of user engagement to Twitter.