Tahm Kench Glitches/Bugs (Gameplay)

I've been playing Tahm Kench constantly since he was released, and i've managed to find a few issues. 1) The first was his Q + W combo, it doesn't specify if it does or doesn't but, When you use it on an appropriate target mob, it only takes the Q's mana, not both. so instead of it being 140 cost combo it only takes 50. 2) This glitch just happened to me in my last game, but on more than one occasion. When i'd devour Karthus, he'd still be able to cast his skills on me, defile for obvious reasons but, it was his Lay Waste he was using from within the devour.
3) I noticed in about 4 of my 10 games, if you devoured a neutral mob and tried spitting it immediately, it'd glitch out and drop the neutral doing no dmg and then making the mob temporarily un-killable. Happened specifically on Blue & red buff minis. 4) I was in a game with a Musketeer Fiora, I could not use devour on her, like she wasn't even a target. Tried several different times with no success.

Just a few things i have found since playing him in 10 matches. All on Summoners Rift. I don't record so I have no footage or links for it. Most should be easy to duplicate with expected same results.