Hep!!

When the drain code says:

+1(damage level + 1) Lightening bolt fx

the your target number to resist the drain is power level/2 plus 1,making a power level 6 lightning bolt target number 4 right?

But the damage level part of the drain resistence test? How does that work?
Do we stage the damage level by 1 making a lighning bolt 6M drain resistance 4S?

Topper

That's correct, on both counts.
For sorcery, base drain is half the force of the spell, rounded down, and the modifier given for the spell's code. Fireball (and most combat spells and elemental manipulations) is a variable damage level spell, so when you pick the damage level (i.e., M), then the DL of the drain is that DL + 1, or S.