Pomegranates are tough trees. They will grow in some of the most inhospitable and harsh soils.
They don't want to be a tree --- they want to be a bush. They sucker heavily from the base, and if you don't prune that stuff back regularly, you will have a mess of tiny, spindly little
root suckers that don't produce anything of value. So don't be afraid to thin your tree a bit to open it up, and aggressively clip all those suckers off from the base of the tree as they continually sprout.
I've trained my pomegranate to be a single trunk tree, in spite of its desire to be a bush. Under it, the guild is chives, nasturtiums (which you mentioned), ginger (which doesn't like full sun, so if you plant some ginger, plant it on the shady/north side of the tree), aloe vera (also not a hot sun lover -- north side), and then I let vining things creep under that area (watermelons and cucumbers do well in that area).
Mulch, mulch, mulch, mulch, mulch. This will help it extend its root system outward, as the mulch will keep the soil soft and moist.
Thin, thin, thin. Pomegranates can be a pain to thin and train because they have those sharp points on the ends of the branches. Wear gloves.
That ants are a pain in the ass. But with a single trunk cleared up from the ground, you could put a tangle-foot barrier around the base of the trunk to keep them off. That's why I've pruned my tree to be a single trunk. The first scaffolding branch isn't until 4 feet up the trunk. But, again, that's why it suckers so aggressively from the base. In both this
thread as well as your other one, its apparent that those trees haven't been thinned recently. Even though its spring, I don't think it's too late to get in there and thin out some of the spindly branches. Open the trees up a bit. Here is a great
video of how to prune.
Finally, thin the fruit aggressively. On your small tree, only keep 6 or so fruit, and pick the rest off. Otherwise you'll not get anything of decent size. You don't want two pomegranates touching each other (
side by side on the same branch), or that is where the ants seem to get into the fruit. A single piece of fruit hanging by itself will be much more pest resistant.
I need to get on the ladder this weekend and thin my pomegranate tree. The fruit are about the size of a small walnut now, so it's time to do so. But it's raining heavily today, so it will have to wait for a day.
Best of luck --- I really like what I see in your pictures (both in this thread and in the other one).