Hey Josh, the mono send to a stereo delay is the same thing I do too. I normally create a mono aux bus (which only requires a mono input), and then insert the stock Pro-Tools delay ("Extra Long" or whatever), the mono to stereo version. Set the delay to 100% wet, a quarter note delay or even a half note might be good depending on the tempo of the song, and then in the past I would set the delay milliseconds off from each other by about 50, and it never seemed to cause any phase issues, and then you get a wide sounding delay. More recently I've shied away from that last detail and gone in favor of having a quarter note in one ear and a half in the other, but it's tricker to get them to decay and vanish around the same time since they're different delay lengths. Anyway, I aux send each of my vocal tracks to it, and I find it easier to keep the aux sends always unmuted, but just automate the level up whenever I want delay. Also, don't be afraid to throw an EQ on the Delay aux and remove some of the low end and high end, which helps tuck the delay back a little bit so you don't hear the "s" and "t" sounds as prominently. Getting some of that low end out of there will probably help with your issue of things getting too loud when the delay swells in too!
Actually, on my latest project, I put the Massey TD5 on the delay aux first (mono), and set it up so that it's pretty dark/kind of saturated sounding, then put the mono to stereo delay right after that (but more subtle), and it turned out really good.
