He was at one point, when both Tesla and SpaceX were early in their lifetimes and bleeding money, on the verge of bankruptcy and (from what came out from his ex-wife) a mental breakdown.

He's risked far more than most investors, including bailing out his own companies (SpaceX and Solar City) by taking personal loans against his stock in others that were doing better (Tesla).

If he hasn't infused the cash, SpaceX at least would have failed. There were a number of finance articles about it at the time "questioning" the odd moves, but paraphrased from Musk, 'If investors are risking their money, shouldn't I be risking mine too?'

If your metric for "enough" is "work to literal death" then I expect you'll continue to be unsatisfied.

Space X was a Falcon failure away from shutting down. Isn't that risking reputation enough? He's selling the world the vision of Falcon Heavy, BFR, Mars colony. Any of that fail and he will be known forever as an ambitious but failed businessman.