chromatic V.S.L.
General mountain dulcimer or music discussions
I have, and prefer, chromatics. The one I use the most has 23" VSL.
If you can play on a 25" VSL diatonic, you can play a 25" chromatic. The frets are the same distance apart, just some are missing on the diatonic. It should not be a problem unless you play up the scale alot, eg. frets above 10 on a 25" VSL
It would probably help understand this by comparing fret spacing between different VSL at the 'tight' end. There's really not much of a difference until the VSL's are significantly different.
This is a good calculator for comparing.

Instead of high to low, dAD, use low to high, DAd, it is more conventional for MD. For the other part of your question, always pluck the string just before turning the knob on the tuner. That way you know when you tune in the correct direction. As far as the F# A d, that would require a string change. You may be thinking of DF#A which needs different strings also. If you are tuned to DAA, just tune down, loosen, the middle string to F#.