1. I think you should consider dropping your first product. If it isn't bringing in good revenue and it's eating up your development time, you might be better off with just your mobile options. This would also handle #3.

You should pick a stable mobile framework to use (since I assume you don't want to go native). Make your backend code as modular as possible (for accommodating changes to their API).

If you're able to do a significant rewrite, I would decouple your data from your logic as much as possible. Write it with the option of offering it to your competitors as a mobile platform.

2. No, if you can reach profitability.

3. Focus your marketing on your mobile product. Devote your time to marketing and sales. Set a profit goal for the near future (well before your cash runs out). If you don't make it, write an API for your app's backend and offer it to your old competitors.

4. If you aren't 100% committed, then you should quit.

5. How much money do you need right now to stay afloat?