You ever seen how hard it is to squeeze the handles on that tool. Much easier to use long bolt a washer and nut. It works just the same as the tool pulling the bolt outwards just like the tool pulls the threaded rod fixture.......
I also have the Amazon Tacklife tool for about $25 back in 2017. Bought it when I added the armor to my JK. Yes, the handles are hard to pull but it can be done. I usually set them and then use some leverage to pull them tight. Have not had one come loose yet.
As for the hex hole in the bed, my aftermarket tonneau didn't use those holes but my ham antenna mount did. I simply took a drill bit and rounded off the corners of the hex hole and used a standard round M8 nutsert in the hole. It holds just fine. Used a standard M6 nutsert in the bottom hole.