Hi & welcome to Gardenweb!

What you described sounds like what I would do in this situation. As long as the plants are getting the amount of light and moisture that they like, what you've described should spur these plants into some serious new growth. On brand-new growth, sunburn probably isn't possible and if they were my plants, I'd be willing to let the old growth burn if necessary to have the plants in as much sun as possible, all day.

Separation of the two plants probably isn't necessary from the plants' viewpoints, but no reason not to if you just want to. Sounds like a good way to have 2 or 4 Gardenias instead of 1 to me. In the long term, do you want to care for multiple pots? If yes, go for it!

Do you want to try making new plants? Where are those pieces you trimmed off?

As long as your soil isn't muddy/soggy/without any air pockets within, as big of a pot as you would like to use is fine. It sounds like Gramma knew that.

What Purple said!:_-)

Hello Purple:-)) Getting ready for over 2 feet of snow, actually, I'll never be ready! Thank goodness it's already Feb. and I don't have to wait the whole winter for it to dissappear.