Regarding his risks on going it solo, you're spot on! In his AMA he called out attempting to hire but pulled back afterwards. I'm assuming it was a poor hire so I'd focus on learning what went wrong and trying it again. Even at just a couple employees, he could grow while preserving his massive profit margin and gain the ability to take time away or weather an illness or family mishaps.
He even mentioned he maintains a full-time job to hedge his bets. If he's keeping it because he wants benefits, I'd think it would make more sense to invest in those himself. If he's keeping it because the work is minimal and the reward (pay) is high enough to offset the revenue from what X number of additional clients would generate, I'd say that could make sense as well. Very specific circumstances.