It looks like a cool plant! That pot does seem small. Maybe you should repot. I don't know much about this genus. I only grow one of them.

You can repot anytime its warm. Two years ago, I potted two identical rooted cuttings of this plant - 1 in gritty mix, and one in Miracle-Gro moisture control. Both in identical large pots - 15 gallon thick walled plastic.

Both plants did exceptionally well, and when I recently unpotted them this spring, the root systems were similar and filled the entire pot. Frankly, they got a bit too large. No discernable difference between the two.

The plant can survive dryness because its a succulent, but it will grow and flower congruent with how much moisture and fertilizer it gets. Obviously that doesn't mean overwater - use the finger test if you like. But don't treat this like a standard cactus either - it's a rainforest species.

It can't take full sun except in the morning, but it should at least be in the brightest shade location possible. Eastern exposure is ideal. More light = better growth and more flowers.

There's an often repeated myth that this plant only flowers "once a year". This is primarily because people use it as a houseplant in dark areas. With adequate light and other conditions, the plant will flush continuously from early summer to fall. The entire plant can be covered with blooms.

I have a similar cacti growing in my own rendition of the Gritty Mix, adjusted for plant size, location of the pot, etc... it's growing very well, and seems to like the better drainage and moisture control afforded by the medium type used.

If the plant has filled its pot with roots, I might re-pot into a container that's of appropriate size... perhaps a couple of inches larger, but not too large... taking into consideration the moisture retention of the medium you're using.

I tend to keep my cacti a bit on the dry side, but my climate conditions and environment are very different from yours. But the beauty of mediums like the Gritty Mix is that it's almost impossible to over water... and in your climate, you may even want to adjust your mix to give it a tiny bit more moisture retention.

If you do decide to re-pot, make sure to keep the plant out of direct sunlight during the process.. and afterward, allow it at least a few days to adjust to its new home, keeping it out of the full blast of the hot sun. Once it perks up from its re-potting, I might introduce it slowly to an eastern exposure, morning sun being kinder than the hot blast of afternoon!

I grow my cacti indoors, in an eastern window... and it seems to be a happy plant!