matyr spell modifier (how much should it be?)

I have a player that wants to start to research divine spells that harms him in exchange to being of lower level.

the "martyr modifiers" that he has in mind are, risk death (save vs death after using the spell), trasfer damage to yourself (you suffer what you heal), permanent atribute sacrifice and suffer random badness (aka mortal wound table or tampering with mortality table).

what i have trouble imagining is how much will those modifiers should be.

Well, I think we can safely posit that it shouldn't be just as much of a discount for doing it to yourself as it is a cost for inflicting it on others.  Having the ability to decide the time and place makes any disadvantage more manageable, and therefore the potential for abuse could exist.  Other than that I couldn't say for sure.