Leslie, I'm happy hearing your citrus no longer have mites. It takes work, but with effort we can rid pests.
Leslie, even if you wanted to repot, this isn't a good time of year to do so. Spring/summer is best..
How small do you want to keep your tree? Or how large do you want it to grow? Remember, potted trees never reach their full height. So, even when you do decide to repot, it will grow, but shouldn't get over 6-9'..especially since you're in a cold climate..I'm not saying it's impossible, but it's rare.
What size pot is it in now?
No need to fertilize either..Wait until March..or if you have a 3 month fertilizer, give one last feeding..more fertilizer = more growth.
People care for plants as they see fit..some ppl feed yr round..it's a matter of opinion and experiences. In all the yrs I've been growing plants, and numerous books I've read, they state it's not a good idea feeding (most) plants in winter, especially if you're in a cold, gloomy climate..all you'll get is spindly growth..But some ppl feed yr round w/great results. Growing plants is trial and error..In my opinion, I don't want to take chances, so the majority of my plants do not get fed in winter..those fed in winter are African Violets, geraniums and tropical hibiscus.
Keep an eye out for mites...Toni