So, that's about 1 year of revenue at 5K cars per week or roughly equivalent to their revenue last year. Or half of that if they manage to double that to 10K per week, as they seem to have promised. That doesn't sound like an impossible situation to me. Unless I'm missing something, a default on these debts is unlikely and given the numbers, access to more capital should be feasible. I agree that these are high risk investments though. High risk and high reward go hand in hand of course.
Elon Musk may owe a little money indeed but he's also a shareholder in SpaceX. I'm not up to speed on how much he owns of that exactly but I believe it is a fairly large chunk of that company. And given the amount of rockets going up lately, his shares are probably worth quite a bit at this point. Magnitudes more than the 600M you mention, I imagine. So, I don't think a personal bankruptcy is that likely for him any time soon.
Tesla 'lost' money investing in production capacity, R&D, opening up a huge battery production facility, etc. That's not wasted money unless demand for utilizing these to full capacity disappears. As it is, the opposite seems to be the case. Tesla is talking about opening additional Giga factories even. That will cost more money of course but I think they can make a case for that being a good investment given demand in their products.
That's perhaps why it's stock valuation is so high: shareholders are expecting these investments to translate into revenue and growth. People that shorted Tesla seem to be getting a bit nervous about maybe ending up on the wrong end of that bet, which could end up being an expensive mistake for some.
Boring and Solar City are interesting wild cards. I think owning Solar City is not necessarily a bad thing for Tesla. Solar panels are in demand and Tesla seems to consider charging infrastructure as part of their strategy. Also up-selling batteries that they produce to people that install solar panels seems like a smart move. Unless there's something wrong with their product, I see no reason for that to fail. They do seem to have acquired a bit of a cost overhead problem, which they have been fixing through layoffs. But other than that, this could very well turn out to be a pretty good bargain.
Boring seems like a weird project at first glance. But it wouldn't be the first side project that Elon Musk is involved in that turned into a real business.