Even though my advice is very basic, but it works. When you play sloppy just slow it down at a tempo that it isn't sloppy. Keep praciticing at this tempo and gradually speed it up, only if you keep the rhythm tight and right!
When I started playing Metal I only kept playing out of my capability and was playing really sloppy! When I slowed things down and took my time it was really improving!
For strumming I would like to suggest a DVD that really was about everything I needed for figuring out strumming. Most important thing was to keep the hand moving and counting (depending on 8th note strumming, 1 & 2 & 3 & 4 &, or 16th note strumming 1e&a2e&a3e&a4e&a ).
But this DVD was from really awesome tutor from London, you may perhaps know him from Youtube, his name is Justin Sandercoe.
http://www.justinguitar.com/en/PR-007-Strumming.php
Got me rid of every strumming problem I had. First I was nicknamed mister robot arm but after that I really improved. It also got me rid of thinking the down up down up way of thinking of strumming and rather feeling the strumming pattern. You can learn LOADS of strumming patterns but I think this DVD covers rather the technique behind strumming and that's WAY more important then learning 2000 strumming patterns.
JJ
Edit: But since I'm not a full access member here, maybe a teacher or someone else from this website can guide you into some strumming lessons on this website :-)