I just called the curb strap police!! They are on their way to pick up your horse and all your tack!!! (LOL)
As long as your horse doesn't mind, using that curb bit and strap is OK. It may not be acceptable in a show but for schooling or hacking, it is just fine, especially if that is what he is used to. BTW, you know that you have to neck rein him with that bit - not direct rein.
I like your stirrup holder. What I used to do was to take the excess stirrup leather and run it around the step on the stirrup to help hold it. That way I didn't have anything extra to carry or lose.
Regarding direct reining with a curb bit: It's not bad for the horse, but it's harder for the horse to understand since you're adding leverage to a bit that has no joint, it's not a clear signal.
If you want to ride with direct rein on your horse and really ride English, a new snaffle is usually less than $20, and is worth the investment. I suggest a double joint rather than the usual single joint.
Although the article concerns the Tom Thumb, it pertains to all shanked bits. Just because it is commonly done, does not make it correct and can easily be related to problems that the rider attributes to other things.