Tried that with a screwdriver. I think the insert inside
is spinning, so if I do succeed in removing the drain
bolt then I have another problem with the loose insert.

I did the patch today and it appears to be holding very
well. The plastic plate is glued with a special high temp
RTV by Locktite and there's a large diameter O-ring
surrounding the indent for the drain plug. From the O-ring
outward is solid RTV holding onto the drain pan (which
was roughed up with sandpaper and degreased thoroughly).
A bottle jack held a 2X4 against the plate while the RTV
set up and I have a heat lamp on the plate right now.
The whole thing feels very solid and there's no leakage
at all. I don't think the fluid can make it past the O-ring
at all .. and even if it did, there's be a solid inch of
this RTV for it to penetrate.

Got my fingers crossed. Wish me luck.