The area was always going to be replaced with tile, so I just ripped up the hardwood boards, but I'd like to know how I could have removed the adhesive effectively.

I don't want to waste his time, my realtors time, etc if this will just be tossed in the trash.

My end goal is to sell it after the rehab, I just didn’t want to waste anyone’s time making an offer lower than what the bank took it back for if that just doesn’t happen in today’s market.

My question is this : am I fooling myself and wasting the sellers time or is there a way I can still close this deal?

If you have a slab you'll need to sawcut it to get a 4" waste line for the toilet installed and tie into existing waste line system. 

The best way you could benefit them would be referring your leads that don't go the wholesale route to them, but to make this effective you may want to partner with a newer agent.

The split roll won't effect any residential real estate.

DO NOT WASTE YOUR MONEY....Speaking from experience!!

For example, some agents have asked me to be preapproved by a lender, I assume they want to make sure I'm serious and not wasting their time.

But its likely you are simply overestimating the effect of an inquiry.