Agree with this. You've done a cracking job in some very harsh light there. You've got down to Alfi's level which has made a huge difference.
Overall I think #6 is the best of the selection - but only because you clipped the legs on #3! It does a good job of showing him out and having fun.
I'd be tempted to crop #3 into a vertical portrait and see how that looks
Oh, and for the form max size should be 800px wide