[LazyPup]

Cutting the old pipe out was ok, but he should have replaced it with a length of PVC with a sanitary tee to connect a waste arm to the new PVC trap.

It is very important that the vent be connected, otherwise the tub will not drain properly and when it does drain the water in the trap is sucked out and allows sewer gases to enter your home.

The new section of PVC can be connected to the existing metal pipe with rubber Fernco connectors.

You could install additional foam,,just be sure to put some blocking in to keep the foam away from the pipes. Plain corrugated cardboard would be enough to block it till the foam has a chance to set.