I cannot tell you how to winter manage your hives. I am in temperate coastal California. Even in my mild climate, going into winter with marginal colonies will result in unnecessary losses. Build up your weak hive to what is considered winter-thrifty for your area, and that means equalize your two existing colonies.
Making splits has an element of art and craft knowledge, knowing how far you can push the bees and when. Beekeeping is a long-term process, and it appears you are trying to "put the cart before the horse".
Learn how to keep bee over-winter, and when you have successfully mastered that skill (and it appears you haven't yet), then it is appropriate to learn the arcane skills of making increase. Start with the easy divides: new hives with purchased queens at the peak of spring increase next May (last week of April in my mild location). Master that skill, and then move on the difficult and fraught process of doing emergency splits in the summer.