Dutchwest FA224CCL - Couple questions?

[Jimmievt]

I was recently given this stove, a Dutchwest FA224CCL. I'm hoping to swap it out for my Englander steel stove to Lord willing achieve a longer burn time with the cat, cast and slightly bigger box. So far I have replaced the door and glass gaskets as well as the top plate gasket (holds the cat probe). This morning I got the top off it (thanks to a comment on this forum which talked about the connection on center front under the top) and today will work on the flue gasket. I've ordered a new cat and the Interam gasket for the cat. My questions are:
1. How concerned should I be about my "oval to round" flue? I've seen some chatter on that issue but don't really understand the issue.
2. Rope gasket or furnace cement to put the top back in place? I like the idea of the gasket but am aware it was cemented in the past.
3. I noted in the manual information regarding "double wall pipe" transitions "needing to be on an approved list" or something. Concern being pipe heat potential.
(my setup is 8' of straight steel single wall stove pipe into a transition to larger exterior double wall stainless at the pass through. The existing chimney was done by a local reputable company about 12 years ago). If anyone can shed light on this potential issue it would be greatly appreciated.
4. Some minor surface rust in a couple spots, stove paste or paint after steel wool?

The fire pictured was run outside last night to burn in the gaskets i put in. Cool little stove!