It's possible the units just been monkeyed with a whole lot which wears the edges, so long as the grommets around the bulbs arent worn you should be in good shape. As far as it snapping together they do that for ease of bulb changing (yeah it seems goofball). So long as it seals well..... bear in mind so long as you can access the bulb from either end to change you should be okay.
Running 24/7 I'd expect about 6 months of useful life and another 6 of semi useful but I'm not a bulb jockey, thats just what they use in the labs I service for their UV sterilizers, if it's good enough for US pharma it's good enough for me I suppose.
As far as pods, it's all contact time, chances are you'll never get a long enough contact time and recirc rate to wax anything that large, you'll stun and stunt them but they'll be fine. Go with the separate pump, feed it off the
fuge and back in and leave it underneath, out of sight out of mind. If it goes wacky you can just unplug the pump and be done with it. Typically I only run UV when I have a reason to and this lends a hand to it.
If the unit leaks, you can run silicone around the edges pretty easy and it will only be a slight pain when changing the bulbs (as you'l have to strip it off and re-silicone it) but all in I think you've got a decent unit.
Keep flow as low as possible otherwise it's moot point.
FWIW I run all my culture water through UV on a recirc for several days before I start my cultures, it's been an amazing resource at keeping bacterias down and allowing my cultures to grow with less competition, aside from that and the occasional outbreak of some random bacteria in a display tank, I cant think of too many daily uses for one. Best to hook it up to it's own pump and leave it be, run it when you notice issues and leave it off most the time!