Fluid coming out of bellhousing not possible and still drivable. I would take a wild guess that its either the front seal or o ring on dipstick.
As for the vibration need more detail. Was motor freshly built? by you? or someone else. Is the balancer and converter both externally balanced? Is...
What kind of vehicle is it in or out of? If it doesnt have a rear cover it is either an 8 3/4 or a ford 9. On the drivers side of the carrier, scrape all the grease off and look at the last 3 number. Should be a 741, 742, or a 489.
One thing that i did many years ago and havent had a leak at all, and have changed the center section many different times.
Eliminate the rtv. I made a gasket out of an old piece of linoleum left over from the kitchen floor.
:thumbrig: