After a shower the toilet floods and slowly drains during this process the tub gurgles. Could this be the Tom's waxed doughnut or the vent up through the attic/roof? Thank you for your time and expertise!
Gurgling from the tub drain and/or slow draining showing could be from either a partial blockage in the drain line OR a venting issue. However, this should not raise the height of water in the toilet bowl assuming it's at the same floor level. The water level in the tub/shower would have to back up to an equal level for that to happen. Unless of course you're flushing the toilet during or shortly after a shower.
Sounds like a partial blockage in the outflow pipe and a blocked vent stack.
As the sewer fills with the water from the shower (due to it being partially blocked the water cannot quickly escape sosit floods) the air displaced by the water which air would normally escape through a vent (such as the vent stack) is not escaping, this causes an in overpressure in the sewer, and behind the trap in the toilet, raising the water level there.