He has a really big, scopey jump to work with :) I think when you are on him, he will be able to control his stride a bit more, with a little help from you of course. Nice horse though, looks very honest :)
He doesnt seem to be throwing himself over the jumps. He just seems green with regards to jumps and considering this is the first time you have put him over a jump I think he is doing well.
He didnt balk or even look like running around the jump which shows to me, a very willing attitude. All in all he seems to have ok form and there is definitely something there to work with :)
As mentioned though I would have a vet confirm that he is sound in his legs before jumping too much. After doing the math with the times you mentioned it seems he was retired around age 7 which is a good run for a racehorse. I would assume from this that he retired from age rather than injury however there are the pin firing holes...whichever way having a vet give the all clear would be good as well :)
He looks like my thoroughbred did when he started to learn to jump--very awkward...but once he learns to put his legs in the right places, you've got a cute little horse! Like NittanyEquestrian said, he's game and that's what matters at this point!