I don't know about the cracks, but I would not use superglue. It looks to me, from the close up pic on page 1, that you didn't break the strands of sinew apart fully, like they are still connected too much at the ends. I've tried keeping sinew strands thick and found they do not sit down well when drying. Better for me was to tear the sinew into as fine a strand as possible, like horse hair. It will comb out and lay down better.
I don't measure anything but I pour a pile of hide glue into a cold crock pot and start adding water while stirring. When it gets thick like something like thick yogurt--not peanut butter, I let it sit for 20 mins and then put the crock pot on 'warm'. Eventually I turn the crock pot up to 'high' and stir and look at it and judge whether I want a little more water or not. It will thin when hot, of course, but you want to be able to grab your bundles of sinew out of the glue and have the glue drip off, like you're dipping in paint...not so thick that you have to scrape it off.
I have a thermometer in and out of there at times and I don't let it go over about 170F, ever, and try to keep it around 140F when I put the sinew in.
I've never done more than one layer so I can't speak to when/how to do the other layers but I would let my stave sit for at least 3 weeks, in any kind of conditions, before stressing it. I might remove excess sinew from the sides or whatever, before that, but no stress.
If you skipped any of my steps I would blame that for the cracking, otherwise I would blame the glue itself. Because I don't like your thick sinew and because of the multiple layers and the cracking, I would start over. If you don't really care that much about this bow then I might shoot the crap out of it and see what happens.
s
