Yes, very complicated. I'm glad you've had a chance to read some more & came to the same conclusion about Flagyl versus Panacur for hookworms. You still don't want to "burn your bridge" with the vet (since some doctors- of all kinds- don't take kindly to our input & instead expect us just to do as they say) so it puts you in a tough spot- I sure get that. It's wonderful to find a doctor (or vet) that sees their patients as part of the "team" but they're hard to come by.

You may just have to "follow your gut" on this- I'm sure you could find reasons to postpone going in for testing this week, if that's your choice. On the other hand, he did eat willingly, right? So no reason to think he won't again- but it would be really nice to know if he fully keeps this meal down without "provocation" from the vet. If that was me, I'd be more willing to bring him in for the test ("3 days after a successful small meal") after he's had at least one more such meal (assuming he keeps this down). If he was my snake, I'd really want to see a little more food in him to keep up his strength- if you can stand not knowing for a little longer (ie. the crypto test). Especially since you mentioned how much weight he's lost.

It's really a tough job to be a vet- they likely feel pressured to get the pets we love healthy as soon as possible- only with snakes, sometimes I think they try to throw too much at a snake's fragile body all at once. But that's just my opinion & I'm not a vet, so there you go- it's your call. And only you know his current condition (as far as how thin he is). If you can, be honest but tactful with your vet with your questions & hesitations. Listen with an open mind too, but if it still doesn't seem right to you, you'll have to be the "advocate" for your WLP.

As far as this possibly being any sort of blockage (debris or tumor or abnormal GI tract), the vet could do a scan for that, right? Pricey though, if it can be avoided (medically helped instead).