hey, sorry for late reply, ive lost passion for this game for some time, but im back at least for a bit
so to answer your concerns:

1/honestly, not bad idea, ive kinda forgot about this when i was creating the mod so i worked around with the sickness strength to give you a sence of difficulty

the mod is deafulted at comfortable settings where if you have severe wound you have to change the bandage or you risk dying, however its forgiving enough to not be too hindering

2/id have to look into it, as implemeting a healing reduction was quite a challenge, but it might be simple, just depends on how they coded it

And increasing the dirty bandage time in relation to first aid just doesnt make much sence to me as vanila increases the bandage duration already, which is good enough on its own

3/i havent playtested with many mods, but i havent found a issue so far with any, but i can suspect that mods that do similar things might cause issues, see First Aid Overhaul, but i dont think people will install both of these at the same time, as mine is more vanilla oriented and First Aid Overhaul, well changes a lot to not be considered vanilla anymore (imo)

edit: just found out about First Aid Expanded which is a bit more vanilla styled than the one mentioned above, so if youre looking for smth with a bit more depth than something simple as this, that might be your choice
also, dont combine those mods together unless you wanna be eradicated the second you get an infection

4/in this mod they add sickness as well, it takes quite some time to tick in, but all is changable in sandbox settings, i dont think its necessary to increase the pain