Sorry that happened to your Blanksenship plexi!!!! I know that's your favorite amp!

I had always heard that the 32 ohms impedance was a bridge too far for Marshall amps back when the HO was popular and there were quite a few stories of amp issues.
I run my amps set to 8 ohms into 16 ohm loads, purely resistive or reactive loads or into my attenuators set to 16 ohms into a 16 ohm cabinet all the time with no issues for alot of years now....Knock on WOOD!

You also have to remember that running the amp full out into a load will stress things like the output transformer regardless but I think the Fryette is a good move, plus it has a loop. I was always told that setting a Marshall Output transformer on 8ohms in to a 16 ohm load helps ease the stress on them when running them at high volumes.
I like the PS100 because it has to channels where you can set the volume different one for rhythm and one for solos and it's footswitchable, that's a really nice feature IMHO!
I think the famous Jose load box was 20 ohms according to most sources.