If you accept funding to do something to help the world, you're not helping the world unless you're underpaid, and the degree you're helping the world is proportional to the degree you're underpaid.

I'd advocate that you become self-funding ASAP, in a peripherally related field. This has a couple benefits. Firstly, your paid work will require you to obtain some real skills and provide some reality checks - countering ivory-tower-ish tendencies to some extent. Second, the ideas you bring to the table from your paid work will add diversity to the SIAI/LessWrong/existential risks community. Third, you will have fewer structural incentives to defend SIAI/LessWrong's continued existence.