I haven't dealt with mites, but this is my $0.02.
If the b.pastel is as fiesty as you say and you haven't done any treating/handling for at least the 3 or 4 days up to a feed attempt, I would try to time an offering 2 days before you would have to re-apply the PAM.
I wouldn't put off applying the PAM, so if the timing is poor, then just skip.
I also wouldn't push the issue if you do offer and just give a few minutes to try. (If offering live maybe 3 or 4 minutes in the tub if no strikes, and f/t no more than 2 or 3 re-heats and offers). I don't think a brief attempt would add enough stress to be worried by if he won't take it.
#1 priority should be the mites, but I'd give it a try if your timing allows. Especially since you say this one didn't seem to actually have any mites.
If you decide to skip offering a bit, don't be too worried about the weight.. one of my last acquisitions weighed 60 grams and refused an initial f/t offering, and my live feeder source was out of anything smaller than large rats for the following 2 weeks (offered f/t in its place). Despite the missed meals, she didn't lose any weight. (Ironically after her 1 live meal in week 4, she took F/T the following week with no issue)
I don't know if I would say 6qt is necessary just yet, I probably wouldn't swap over at this point, but if you do swap, definitely give some time to settle before offering. Since Deb says to do it, then that's probably a good call. This just my opinion.
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