@Another planet, First off, the wheels and tyres look great! I’m no tyre fitter, but I’ve fitted and removed a few sets of wheels over the past 30 years and just recently removed the original 205/65/16’s off mine, replacing with the same tyres as you’ve got there, on fuel zephyrs and am pleased to say I’ve had no issues after 2500 miles and I’m certain I won’t have any wheels coming off because of the change. In your case, Im sure it was just human error on the fitters end of which they should have but are not admitting fault to. If those nuts where tightened properly, I’m pretty certain they wouldn’t work loose after a mile. It was obviously a eye opening ordeal to say the least. I would put it behind you now though and don’t let it spoil your van fun. But as a precaution, any time you get wheels/tyres changed or fitted check them yourself before you move on.