Painting the inside of a varnished wooden door

Greetings all & newbie alert!

I decided to paint my front door, which is about 30 yrs old and seen better days. It was a varnished wooden door, not the best one in the world even when it was new, so I wasn't sure if painting it was worth it but I went for the Dulux Weathershield system which I heard good things about and so far it's looking pretty decent IMO (so far primer and two basecoats on all around, and one layer of gloss on the outside).

My question is about the inside of the door, which doesn't have a topcoat on yet. I presume I won't need any special exterior paint, Weathershield or otherwise; I'm hoping just standard white gloss would do, or...?

Also, the door isn't very well insulated, which causes condensation to build up on the inside of it during winter when it's cold outside and warm & humid on the inside. Should this affect my choice of paint for the inside? Or better yet, is there some sort of magic paint out there that would actually improve the insulation value to any meaningful extent? And if so, where would I find some, as I'm pretty sure I've not seen any at my local DIY store...?

Finally, when I took the door off its hinges to sand it etc., I noticed that the top and bottom edges were not varnished. My first reaction was that whoever had fitted it many moons ago was just a lazy git and couldn't be bothered with them, but then I thought maybe there's a reason for it - or can I just go ahead and paint all the edges as well with the rest of the door?

Thanks in advance!

 

Sanded, primed, and two layers of basecoat.