1. Made a quick fix to have the raid frames obey the global setting.
2. Fixed that.
3. If you have installed it correctly you should see HP numbers after the mob lost 10% health. By default MobHealth3 doesn't save its data between sessions so you would have to wait those 10% again after relogging / reloading UI. There is an option to change it so it saves its data. Read about it on its page.
4. Range works the same way as it does in (non modified) all other Raidframes (sRaid, Grid, etc...). There is an easy way to check for up to 30y with the UI functions but the 40y check is based on combatlog. This means if you are standing in IF you won't see 40y because others are not producing combat log events. But if you are in a raid and others do something every like 3 seconds they are refreshed as "in range". I know there is other hacks of raidframes out there where every unit in the raid gets targeted every 0.5 seconds to see if a 40y spell is in range but that heavily affects performance and/or other behavior of the frames.
5. I'll put it on my list.
6. On the list but no promises since the UI doesn't send events for it.
7. The squares are colored for type of debuff. For example magic is blue. Non dispellable debuffs are only shown on the center icon but dispellable ones get higher priority.
8. Debuffs always use a new line below/above the buff line(s).