I just thought of another way I use to get aids out - this worked great with ITE aids (custom, hard-case mold): Just push your ear from behind while pulling down on the earlobe. I can do this with just one hand even. It’s kind of like turning a muffin out of silicone cup, if you get the analogy?
It appears you got two different domes, tho! If one is slit and the other not, no wonder you have the vacuum seal. Was it a manufacturing defect, or did your audiologist actually think a NON-vented dome would work in one ear?