Drilling to make it RR is always pref... seeing as there's water in there already i don't think that's an option. I'm aware you're trying to attach the DT to the sump, but you're not i'm not sure how well this will actually pan out and compared to other methods, i'm not sure why you'd want something so bulky in the Display anyways. I watched the vid, it didn't look very professional. I'd rather see a black overflow box with a piece of PVC in it and then that leading to the sump and ect and not this bulky thing. Will it even re-prime itself if power were to ever turn off?
You didn't rub any algae on the scrubber? You're suppose to, that'll ensure good algae growth.