You need to use a different halter than what you are when lunging especially. This type moves and will go up and rub on eye. Get a regular halter for this.
You can see in the photo that it is out of position.
And I too think he is not in good weight, not skinny but I would like to see him a bit heavier.
As for your weight?
I weigh 239, with tack I am pushing the upper 200's easily. And that is too heavy to be riding. So I don't right now. I have a chunky QH, that is 1200 and carries good bone, and my older QH that would be my main riding partner if I were not so heavy is maybe 1000 or so.
I do not ride because it is not fair to put that much weight on an area that is a span. If the back were directly over a set of legs? Would be a different story, but you are sitting over legs...you are sitting in the middle, with no support under you.
And much of the damage our weight does to our horses? Will not be able to be seen. As another posted, they are very stoic. All one has to do is look at Big Lick THW's to see that....horse is in pain and keeps right on going.
Spinal problems will not show up without the diagnostics needed to show them. Most of us will never have an MRI or ultrasounds done on our horses. Most won't even go to the trouble of X-rays either. Cost factors in, vet nearness, and lack of need.
I would step up your workout program for yourself and lose the weight you need to.
And may I say it is so nice seeing someone who is willing to consider that their weight is a problem.
Horses make me a better person.