Keep in mind that X-T3 has a 1.18x crop while shooting 4K 60fps, and the selection of wide-angle lenses is limited. With SeaFrogs, your only wide-angle option is the 10-24mm f/4 in a dome - they don't have a short threaded flat port that would fit the 15-45mm to use with a wet wide lens, and 8-16mm is too thick to fit through the port opening. For macro, they only list the 60mm as supported, and there is no threaded port for it, so you can't use diopters to get better than 1x magnification. Looking at lens dimensions, it might be possible to fit the 80mm macro lens into the KitDive port made for Sony 90mm - they have nearly the same diameter (80 and 79mm respectively) and length (130 and 130.5mm), but I don't think there are any physical stores where you can try it to see if it works.
Also, when you're doing budget calculations, don't forget lights - a pair of 10K lumen lights is the bare minimum for decent wide-angle video. Scubalamp V6K series is fairly popular and well regarded. Then you will need a tray, arms and clamps to mount them, and since big lights are heavy, you will need floats to maintain neutral buoyancy. With a large acrylic dome, you will also need weights up front to maintain good trim, or the dome will float up and try to twist the housing out of your hands.
E-PL10 has access to Olympus and Panasonic library of micro four thirds lenses, which happens to have some very good choices for underwater photography - 7-14mm and 9-18mm wide angle, 8mm fisheye, 14-42mm zoom (very good with wet lenses), Olympus 12-40mm zoom, possibly 8-25mm zoom when ports for it come out, 30mm, 45mm and 60mm macro lenses. The AOI housing for it is fairly full-featured and provides excellent value for money. On the downside, it completely lacks PDAF, relying on pure contrast detection for autofocus, the sensor is an old 16MP model, and if you shoot 4K video, there is a 'heavy crop' applied - none of the reviews I've found mention how big that crop is, but they all concur that it's very narrow. There is also a 10 minute limit on recording 4K, but next to the heavy crop, that's insignificant.
As I mentioned in my response to your other post, now is a good time to look for a used Panasonic GH5 rig. It's a much better video camera than either X-T3 or E-PL10, rivaling the full-frame Sony A7S III (there are pros and cons to both models) and the recent announcement of GH6 should depress the prices on used sets.