They are schooling shows....so use them just for that. Don't go to them expecting to win something as that isnt what they are about. Set goals for yourself such as getting the correct canter in flat classes, and not breaking to the trot. Or get the correct distances between lines. Go to the show with the expectation of learning. The following show, set goals to correct what went wrong at the previous one.
I think your guy is still out of shape (not horribly) and could use a lot more trot work to help get him in shape. If he isnt moving off your leg, invest in a small spur to helo encourage him to do so. Do lots of leg yeilding starting in your warm up at a walk, as well as at the trot and canter. He should be able to go into a smaller and bigger circle off of leg pressure. Don't be afraid to use your crop either when he isnt listening. Sometimes they only need one quick little smack to remind them to listen.
It is never to early for a schooling show.....as long as you are using it for schooling, and not for winning.