engine dying due to electric fan

As to stalling when in going into gear, check your T-port sync
And your PVs. In an Edelbrock, that would be the metering rods. Maybe the 5" vacuum is not enough to keep the rods down, so they jump up and flood the engine.

5" of idle-vacuum is pretty freaky low. It usually indicates: a vacuum leak,a very bbbbig cam,a very low idle speed,or very late idle-timing. Another reason to see 5" at idle is if the gauge is plumbed to the sparkport, and if the primaries are really far open, which goes back to seriously late timing.
And of course there's always a chance the gauge is in error.

And one more thing; if the engine is tuned real sweet and you get the vacuum up to 11ish with a nice T-port sync, and then you put it in gear, and the Rs take a nose-dive, Well maybe the TC is NDG.