If I understand you correctly. You filled the overflow with water and the water leaked out into the display. If that’s correct. It’s fine. Just as long as it’s doesn’t leak out the aquarium on to the floor.
I’m a fan of run what you got. I’ve ran dual skimmer for years before. It will get you by until you find a deal on a bigger one. I have a bunch of large skimmer bodies if you want one. But the magic is in the pump and Venturi. Which I don’t have.
I can stick pieces together. There’s a lot of prep involved. I don’t have a super expensive router. But yeah. I can. If there’s enough interest. Let me know.