ceiling support box questions

[Verdure]

I have two concerns about my ceiling box that I am not sure how to address. It's 25 years old, we are not the original owner/installer.

First is the male interface piece has come loose, it is normally attached by two screws but both have fallen out.
The chimney itself seems to hold the interface bracket in proper position (pressed upwards) but I suspect this is unsafe and want to put the screws back in, however I can't see how to do so without pulling down the round external casing. There are no visible screws holding the casing in place, do I just pry it off? Trying to do this without destroying all of the surrounding wood paneling (it's in there really tight). The only other option I see is to fish the whole thing up through the attic.

Second concern is that even when properly in place there are visible air gaps between the interface bracket and chimney, is this okay? I can't imagine smoke or sparks going up there being very safe, but perhaps the air draw of the open chimney is enough? Photograph didn't turn out well, but you can see that it is not snug.

Apologies for the wonky terminology, this is my first rodeo.

 

[DAKSY]

I’m thinking that you’re going to have to pull the entire length of Class A from above the ceiling support box in order to access the connector pipe adapter…

 

[Verdure]

I’m thinking that you’re going to have to pull the entire length of Class A from above the ceiling support box in order to access the connector pipe adapter…

I think I can pull it up from the attic, just haven't tried yet.
If I manage to get the connector pipe adapter attached properly, should I worry about the small gaps? I wasn't able to get a good photo, but they are large enough for light to shine through

 

[DAKSY]

If that adapter is securely seal to the Class A & the connector pipe is securely attached to the adapter, don’t worry about small gaps between the adapter & the support box.

 

[Verdure]

After a lot of blood sweat and tears I was able to reattach the adapter.

My one and only remaining concern (other than for the mental health of the original installer) is the gaps, the adapter does not fit snugly and there are air gaps all the way around (attached photo shows the biggest one).
I think I described it poorly in my last message, the gap is inside the stovepipe itself, I'm worried about smoke or worse escaping through edges and into my home's walls. Any way to tell if this is safe? (there is some kind of insulation around the wall adapter, hopefully fireproof, that you see poking through)