Yes. I think lower. I've changed my thinking a bit after looking again at your photos. Note the apparent very wide beam width. The rough rule I mentioned presumes a much tighter beam, at least two feet up, more concentrated on the growing area. In effect, a great deal of your light is not getting to the plant. I think you're getting even less effect from that light than I was at first thinking. So, I think you can move it significantly closer.
The maker claims a beam angle of 60 degrees. That means that for the light to cover just a bit more than about 20 inches, which looks to me about the length of leafed portion of the tree from the point of view of the lamp, the distance would be about 17 inches.
So, I think that means you can get the light closer than I first thought without danger to the foliage. And it means that, although we're kind of guessing about light distribution, you can cover the entire foliage from a position somewhat in front of it and about 17 inches distant at the closest point. So, I'd look for a position that would make a 60-degree beam address the entire plant and not much more. I've got a feeling you're going to end up about that17 inches from the plant at the closest point, maybe less, and that there won't be so great a difference between the closest point and the farthest to be a significant problem of insufficient light anywhere.
Just in case, keep an eye on the leaves closest to the light so you catch any browning or yellowing from light burn early. But I think the light intensity is little enough that it's unlikely to burn.
