My dog is very well behaved and I can train him to leave the chickens alone.
I'd be very cautious with that, though.... if you browse the Predators and Pests section of this forum you will notice a recurrent theme of "I was sure my dog was good with the chickens, right up til the moment he ate one of them yesterday'. Not saying some dogs *can't* be trusted reasonably well around chickens but it is definitely risky and if you are new to chickens I'd suggest being especially careful.
Anyways, I guess long story short, do you have any advice for me about putting my chicken coop INSIDE another building? Is there any special circumstances I need to think about?
A big thing is to make sure they have ample natural light (windows, or siding replaced with plastic panels). Obviously you can use lightbulbs to supplement this, or to lengthen winter days for laying, but that's not really a substitute for large windows IMO.
Regarding your plan to make their 'run' indoors, can I suggest maybe reframing the situation as "give them a very large ample indoor area, no need to divide it, and then *also* an outdoor run.... so that on days when you do not want to let them out they will be happy hanging out indoors". In a way that's what I have, although my chickens probably go out more often than yours will... mine have 15 sq ft per chicken indoors plus their roofed runs, so that on days when for some reason they have to be left in or when they simply do not choose to go out, they still have plenty of elbow-room in their indoor quarters. If yours are going to be indoors most of the time during the winter I'd shoot for even more than 15 sq ft per chicken indoors, really as much as you can manage.
Having a predatorproof outdoor run would give you more options, though, not only in winter but the rest of the year as well. It'd allow you to keep the chickens under control at times (e.g when teaching pullets to lay in the coop not randomly all around the property, or when you are having a particular predator problem) without having to lock them totally indoors. Even if you don't set up a predatorproof outdoor run right away due to time/energy/material limitations I think it'd be an awfully good project to plan for when circumstances permit. Plenty of people who free-range their chickens have a run too, and I don't think many of them regret it
Good luck, have fun, looks like you should be able to do a really great setup there,
Pat