Ok, good info.
That little filter is too small.
I'd have 5/8 id at least, the larger the better.
The 3/8 id may have been a restriction and allowing the crankcase to pressurise, hence pushing the dipstick out.
As to the rear seal burning up, either the seal is running too tight on the crank, or lip facing forward is the wrong way.
Some seals have an arrow showing shaft rotation direction.
Do not put
oil in the cylinders prior to leakdown test.
As long as you have no loss past the valve seats, and only a loss of 2-10% into the crankcase would be ok.
More than likely you'll have 10-20% loss with a fresh bore/ring set.
Your compression test looks ok.