hey you can try to use some of that plastic wood, (no really that's the name of the stuff) to fill in, you can use it on those cracks too, the stuff turns to concrete when it dries, you need a belt sander to get it off, but it can be drilled planed shaped what ever , i think its stainable as well.
hey nice deck
yeah that's the stuff once it dries it's like a rock
i use it speringly, make sure you you mix real good all the good stuff is at the bottom of the can
also it's easier to add more than to buldoze down the extra