It is a cute video, and he looks like a sweetheart. Nice attitude and a pleasant way of going.
As for dressage, he's got some things working against him. First of all, he's built like a racehorse (duh! He's a TB, right?) By that, I mean he's built to go hollow or inverted, and he has very little muscling on his top line - going on the aids or rounding up is going to be really hard for him. Second, he has a fairly long back, so again, rounding up is going to be hard. Third, he moves very close behind, which means he doesn't have a good base of support for some movements.
That doesn't mean you *shouldn't* do dressage with him, just that you should be aware of those characteristics and limitations and that he's not going to be an international dressage superstar. Some lower level work will muscle his top line and probably improve the quality of his movement and it might add some interest to your flat work.
I'd also recommend you work with a dressage coach to get you started. Working in dressage with TBs has some special challenges and it's really helpful to have someone on the ground observing. I'd also want to make very sure you didn't do anything to spoil his good nature and lovely attitude.
As has been said in other threads of this nature, any horse can reach a reasonable level of dressage. It is the higher degrees of collection and thus the higher movements which will stump a horse/rider. Almost any horse has the ability to reach medium dressage, however it may not be competitive at this level. I know what it's like to be training tb's for dressage and it is certainly a different can of beans to training a horse bred for the sport, such as a hannoverian. A tb's brain is wired differently, they are far more reactive as a general rule (there ARE exceptions obviously) but usually you need to take things a little more gently when training a tb, when they lose their brain they REALLY lose it, where as a WB tends to be a little less reactive and won't 'lose the plot' so to speak.
As was said above, he may find collection difficult due to having quite a long back, but you will be able to get the basics down such as having him off the forehand etc. But I would definately be getting yourself a good dressage instructor that isn't just going to force him into a frame as getting a long backed tb in particular, to learn how to use his back rather than move with 'all legs' can be a big challenge depending on the horse!!
You can most definately do dressage!! It just might take some extra time and patience. I have a OTTB who is built very similar to Chinga, with his long back and tendency to hollow. Just these two characteristics have made it so much harder to have him rounded and engaged.
I would highly suggest getting a good dressage trainer to help you along. It is so important to have a trained eye on the ground to point things out, and to also give helpful advice.
Just remember this may be a fairly long journey to get where you want, but just be patient and you'll get there eventually.
Also, just so you have something to look forward to here is some before and after pics of my TB....
Before he would travel with his head in the sky and a completely hollow back. With his back so hollow it made for a very bumpy ride.
Now, a year and a half later, he has started to round his back and give to the bit. We both still have a long way to go as he still has a tendency to lean on his forehand and has trouble with transitions, but we're getting there.
Just thought that this would give you an idea of what to look forward to after some patience and time with a good trainer. And also sorry if I hijacked the thread...
Every horse will be bettered by dressage, because it helps them engage their muscles and learn to carry themselves in a way that helps their joints. Find someone that can teach you how to get your horse active and engaged. Having worked with ottbs, I found one of the hardest things to teach was the concept of a half halt, since many racehorses are taught to accelerate when you pull on the bit. so at first, many of the horses seem a little confused that with my half halt, I wasn't actually asking them to speed up, so much as I was asking for the hind end to come underneath a bit more