VOLT Arabic diacritical marks mark on mark mkmk

VOLT Questions for an Arabic font.

Salaams - 5 years and 39 weeks have passed since a group of us started this typophile special interest group!

I am trying to finalize the OT version of my AlQuds font (started in the 1960s!). Some final problems in VOLT:

1- How to create a lookup for a case when two marks are elevated on top of one glyph at a given height. The first mark shifts up OK but the second one overlaps it. There is a separate lookup for Marks on Marks which works fine when the marks are at their "normal" height above the anchor is there a conflict with that?

2- When typing a mark then another - for example a shaddeh then a fatha I get shaddeh and fatha on top. But when typing the fatha first then the shaddeh, the shaddeh comes out ontop making it shaddeh kasra!