How do I handle the "What ifs"?
Frankly, I don't.
Most of the time I just live and take life as it comes. I take care of what I can take care of. I plan ahead as I can, I make preparations as I'm able, and do preemptive maintenance as possible. But honestly the amount that actually gets done is very little.
I think this is part of the big difference between carefully planned out, intentional vandwelling vs. sudden homelessness. With the former you have the luxury to go on the road when you're 'ready' - yourself, physically and mentally, your rig, outfitted with everything you might need, enough of a financial cushion to handle emergencies, etc. With the latter it's *poof*, surprise! You're on the road now, unprepared. Your rig isn't outfitted. You're sick most days of the week - physically with fever, projectile vomiting, and severe insomnia or mentally with PTSD and panic attacks. You spend your last dollar to fix the latest breakdown and then have nothing left for food the rest of the month. This is my normal life. I'm too disabled to take care of myself, so I've adapted to swinging around picking up people who enjoy my company or appreciate the crash pad to lend a hand here and there.
Most of the major "what ifs" posted in this thread have happened to me multiple times per month of the three months I've been living in my van. I'm generally too occupied dealing with pressing present priorities or recovering from recent crisis to concern myself with what else might go wrong. When something does, I take a deep breath, re-prioritize, and keep going.