I covered the garden with leave and grass mulch last fall. Tilled
more in this spring.

Might be too fresh. Ideally, you'd let it compost elsewhere and put
it on/in the garden after a year or so. (I can't tell whether you are
doing that, because I don't know if "leaf and grass mulch" is already
composted or not).

How many inches of mulch?

I will get organic fertilizer this fall and stink up the neighborhood.

Worth a try. For the above reasons I would second the suggestion to
apply in the fall rather than the spring.

Can I also add 10-10-10 to the hole before placing new plants in next
spring?

Quite aside from the chemical versus organic, there is such a thing as
too much of a good thing. If you don't get results with manure,
compost, etc, I would guess you have a problem other than lack of
nutrients.