According to a quick search, it is hardy in zone 6, and it seems like it would like to get larger than being a house plant.

If that is the case, i think some of the slow growth you are mentioning are because it is not outdoors. A passion vine with a bit of sun and space can grow very well without too much human care and intervention.

But if you want to keep it indoors, you might also check the pot. Maybe it's time to repot it. It might also be that the amount of light you think is good is still not enough. You could try indoor grow lights on it also.

However, I would suggest the following. After repotting or verifying that it doesn't need repotting but maybe just additional fertilizer, then let it be an outdoor plant during the growing season. As it dies back down from the cold temps or frost, then bring it back inside for the winter.

I would also suggest that you can try to propagate it and leave the new plant outside for the winter (remaining in a pot, if you wish). Verify that in your desired location, it would be able to overwinter outside.