The only problem with the carriage bolts is that they appear to be standard steel, not galvanized, which is a problem in contact with PT lumber. I probably would have used hot dipped galvanized hex head bolts, not carriage bolts,since you may need to remove one someday, and there is nothing to grip on the dome end of a carriage bolt.
The splits in the wood are typical of PT lumber when it dries, not much you can do about it, and as previously noted, will not reduce strength much. Besides, that is a low retaining wall, so likely no problem at all, other than appearance.
There are some types of PT lumber rated for direct contact with ground, they are expensive and not too easy to find. Most PT lumber is rated for outdoor exposure only, not ground contact. All this means is that they lumber will rot after perhaps ten years, maybe it will go twenty if you are fortunate, so at that point you can replace the wall. When and if you need to replace the wall, you may want to consider concrete segmental block, in my opinion easier to install than lumber, lasts essentially forever, and very cost competitive.
