[AZKen]

OK, I will assume when you blew out the lines you made sure you got good air thru to the other end and you did not blow thru the filters.

Also, on this pump test tonight, if you don't get and flow out of pump, try again with a new hose and no filter on the outlet side. If no luck there either, take off gas cap and try one more time.

You don't need, and should not have, a filter after pump. Only one before pump.

During the sequence of events before and after you discovered tank was rusted, it's possible a line, or a filter or the pump got clogged or partially clogged. It's also possible the pump is bad.
The gas tank can also have a vacuum lock due to it not venting properly. That would prevent pump from sucking gas. I know you say you are getting gat to pump but you can't be sure of that. A partial block or venting problem will allow enough gas to see a "drain out" like you saw. But that is not prove of much. Only way to prove good flow from tank is let gravity cause fuel to flow out the end of line into a container to see the volume. For now, just do the outlet test per above instructions. All tests no less than 15 seconds with good battery and good starter speed. Take out plugs if you want more speed.