As above, I've got someone like this in my team, keeper up, bowls slow away swingers. Personally I try to use him up front for as long as possible, and if someone starts getting hold of his bowling, take him off. I know this isn't much help in your situation, but it might be worth thinking about what time and situation you're bowling in, as certain bowlers are suited to different situations and it doesn't make you any better or worse for it, every team needs a variety of bowlers.
It sounds like you're floating it up, rather than getting through your action. I would suggest possibly getting your front arm in a little tighter and pulling down with it, rather than reaching out forward. This should help you to 'complete' your action and hit the pitch a little harder, as you'll be getting your shoulders and core more into your delivery. It should also help with getting hit over your head. It's always more difficult to hit a bowler off the front foot who hits the pitch hard, and will give the effect of you being a little bit quicker, especially if you do happen to drop one short.
Anyone who has slipped in their delivery stride on a damp pitch will naturally bowl very floaty, as you don't get through your action, if you drag it down, it's the slowest ball ever. It's a exaggerated example, but holds true that if you get your full body through your action, you'll have the effect of being quicker should you drop it a touch short by virtue of bowling a 'heavier' ball. Think along the lines of how Chris Woakes (floaty) is faster on the gun than Steve Finn (heavy ball), but it certainly appears that Finn is faster.
Just my two penneth, as ever, practice anything in the nets beforehand and be confident with it before you go into a game.