Many predators go well in a reef, most don't bother your corals, you clean up crew will likely be on the menu for some. I run some tangs without cuc, they are not 100% necessary. Or you can replace them from to time, it's not that expensive and it gives your fish something to do. To include most of the fish you like I would say 125g is the minimum tank size you would want, any smaller and would want to make adjustments.
Tangs are reef safe and the smaller ones like a zebrasoma or bristletooths go well in small 6 foot tank. The purple tang is arguably the prettiest, but can get pretty aggressive. The harlequin tusk looks menacing but is actually a pussycat except towards some other wrasses, he will definitely hunt down your cuc though. The snowflake eel will cause no threat to any of the other fish you've chosen.
Let's talk triggers, stick with the xanthichthys genus for best success, the bluejaw being the most available and affordable, although I have heard stories of even these munching from time to time. Any other triggers you will have to value the fish more than your corals, regardless of what else you read I have only seen success with other triggers to be short lived, and any real success in very large tanks.
If you are serious about a dwarf lion, if you want to keep him alive more than year, keep in him an observation tank and get him eating a variety of dead foods before placing him in the dt. Target feeding chunks of meaty food will be necessary to keep this guy long term. Any shrimp will be an instant expensive meal. Read through this thread
https://www.reef2reef.com/threads/an-arguement-for-feeding-live-foods.582822/
The toby puffer, a notorious nipper, he will likely munch on your corals, and I would never put one in with my lions.