Good on the judge. Over here it really irritates me that judges will hand out 70+% to riders who ride off the horses head, because they're 'junior' or 'unofficial'.
When a judge gives you low marks, don't go off and have a cry about it and say it's not fair the judge has no idea what they're talking about then go home and keep doing what you're doing and never get any better.
If they give you a low score, look through the test paper, read the comments that the judge has given you and see where you can improve. A test puts you under a lot of pressure so all your flaws will be likely to show. You'll get a good idea of what you need to work on from competition. Compete to train, don't train to compete.
I would be interested to hear what comments the judge gave you for this test. It is ok, your horse goes around with its head down and goes from A to B in a fairly straight line. It's alright. But it's not a test that is going to stand out and pick up the higher marks.
To get a better score next time, you really to concentrate on getting your horse working from the backend up into the bridle. Quit the silly head wiggling see-sawing action, that does nothing but distract the judge and probably make your horse dizzy!! Ride forwards into a steady hand, learn to use an outside rein and how to ride into it. If your instructor doesn't teach this, then find a new one if you want to better your chances of placing. Look in the dressage section of this forum. There are hundreds of topics in there with some great advice that will benefit you.
You say he's improved greatly since last season. Well it's good that he's not spitting the dummy in the arena if that's what you're referring to. But don't expect the judges to mark on the improvement in behaviour, they mark what is put in front of them. And in your case they saw a horse that was being ridden by its head. That is not going to mark well.
Also work on your position to help you gain marks. In canter your arms/elbows flap around all over the place. Concentrate on lifting your chest, allowing your elbows to rest at your sides and keep your lower arm steady to help encourage your horse to work into the bridle. At the moment he can't take a contact on the bit in canter because when he does he gets smacked in the mouth every stride.
Free walk is double marks as MyBoyPuck said above. In the free walk the ears should be level with, or ideally lower than the wither. A clear 4 beat march being encouraged by you moving your elbows in time with the movement of his head. You can encourage the lowering of the head in a free walk by opening your reins out a little while in a test to help you along a little. Make sure you keep a light contact, the free walk does not mean drop your reins.
Keep practicing you're off to a good start. Just don't get shirty with the judges because they didn't give you a blue ribbon when you thought you should get one. Step back and compare the video to the papers they gave back to you and you will see a connection. Try not to look at your test through rose coloured glasses, thinking you are the best and doing it all perfectly is not going to help you improve.