You have done what is called a "slam install"..

Good plan if you don`t care about the safety of yourself or your family.

You need a stainless steel liner from top to bottom.

And don`t expect a lot of heat from that old smoke dragon, specially if you are burning green wood.

If you are going to heat with wood, then do it right!! Or don`t do it at all!!!!!!!

I think you got exactly what you paid for. And old smoke dragon that should have been scrapped in the 90s. Today's inserts are a lot more sophisticated than those old units. Yes, you need a 6 inch s/s liner the complete length of your chimney. You have no draft which is why you have smoke in the house. And I agree, you have put yourself and your family at risk by trying to save a few bucks. Tear that thing out, scrap it, and have a modern unit professionally installed. You will then have years of enjoyment from a unit that was done right.