Sounds like it needs a bigger pot to allow the trunk and root system to develop. IMO Its not a good idea to cut a branch in the middle of its span.

It's your call and it's hard to give advice without seeing a picture of the plant, but you might try to selectively prune one or two of the longest branches before you bring it in (then do the same at the end of the following growing season). Leave at least 12" of a branch 'stump' so it has something to regrow from. Hopefully it will send out two or more tips near the cut. Keep in mind if you cut ALL the branches back you will likely not get flowers next season. So leave at least two branches and tips for flowers. Flowers develop on mature growth, not on the thin, new, soft green growth.

Big, lanky plumerias can be difficult to train sometimes. They want to be trees! That's why I'm trying to cultivate the more compact varieties.