Free??!! Are you SURE he's 100% sound and sane? Did you have him vetted? I'd be nervous - that type of horse around here, assuming it was broken in and quiet under saddle would sell for 5k+ easily.
Have you ridden him yet?
I do hope you got the bargain of the century and not something dangerous or with a hidden health issue. Sorry, devils advocate but having been bitten by sellers on a few occasions I tend to err on the side of caution.
As far as conformation/paces, a video of him moving and a few shots of him squared up will be extremely beneficial. You can get a good photo of any horse moving if you're quick enough - horses with zero bend through the hock normally can have a moment of excitement and exhibit some bend.
I'd love to see some video, as I suspect he *may* struggle to lower behind in the more collected work. But I may well be wrong. Video would be useful!