Ok first off position check.
-Check that your heels are down, really stretch through from you hip down the back off you calf and try to keep your lower leg on and stedy, squeeze when you need to but down pull your leg back every stride to push him on.
-You elbows do look a tad straight but not too bad
-and yes you need to look up and use your head as a balance, turn it when your changind direction, look to where your going
Your horse has a lovely walk, try to get it a tiny bit more active.
Shorten your reins a tad and throw in some half halts with your outside rein and you ask him forwards, just to remind him to use his hindquarters.
Make sure your inside leg is on the girth on your circles, everything kinda flops around and that's where you get balance issues. Your inside leg is there for him to bend around and use as a support frame (though not leaning on it!) and balance.
Your hands look fantastic and even and steady, but watch you don't lift them with your body when you ride, many riders do it
Your thrusting a lot as you rise, heels down, legs on and use your legs to push him forwards not the thrusting of your hips.
You guys are looking pretty good so far! I'd love to see some more soon to see how you've improved!