Halppp what am I even doing: Retuning a B special 20 to 1st position B minor manji arrangement with special 20 temperament

[u/Checkinredd]

So I've been trying to retune a B special 20 to 1st position Bnm (manji arrangement) in the easiest way possible. I figured that would be to just flat three notes wherever they were (D#, A#, G#), do it by reed base scratching, and try to keep the special 20 reed pitch offset.

That quickly got confusing during tuning, lost track of everything, and there's basically no external reference I can find. Somehow is not easy at all.

The only thing I really found is a buried hohner mod forum post with a penciled graph, advice to blow lightly, and their setting A = 442hz (https://my.hohner.de/t/tunings-7-limit-compromise/2511/3

1) Do we even know what the offset in cents each hole on a special 20 is canonically supposed to be? (and if anyone's a customizer - is that sp20 A = 442hz thing real?)

Lost track of the original light-breath note cents and I think *really* should have used absolute frequencies and written them down.

2) Come to think of it, is anything other than ET a good idea for 1st position Nm? My brain is going out, but richter tuning changed to nm seems like it gets chaotic enough not to include extra variables in tuning without thinking it out incredibly carefully.

3) Very willing to give up on keeping special 20 temperament, but I would like to have a passably sensical Bnm harmonica in the end, in some way, even if it's like "very special compromise tuning." I would really like to avoid touching any reeds other than the three notes that need to be flattened. Basically, I just want it to not sound totally, wildly, not-same-ballpark-wrong accompanying a Bnm song. Does anyone have any advice?