If you're ok with a couple of tips, the set will have come as a result of a few things:
Firstly, where is the set happening? I wouldn't be too surprised if you're getting most of the set at the fade on the bottom and just above the fade on the upper limb. This is because those are the areas that are working the most on your tiller. The bottom limb is pretty stiff apart from right on the fade itself and 2/3 towards the tip. The upper limb is much better, but still working more just above the fade, rather than through the whole limb.
The other main reason for getting the amount of set you've seen with this is tillering method. If the limbs weren't bending perfectly evenly (and we can see that they weren't from the full draw pic) at any stage during the tiller, but you pulled the bow further anyway, that will over-stress the areas bending too much. This is a guarantee to get string follow, so just bear it in mind next time perhaps. Basically, the second you see one area of a limb not bending evenly or bending too much, never pull the bow further until you've corrected that area. It's super tempting to think "I'll pull it a bit further to see if it looks worse or gets better" at which point you've done irreparable damage and will end up with set.
The final reason for set (and not at all likely with a board bow unless you're unlucky) is using green wood. Wood that hasn't been seasoned, or has too high a moisture content will follow the string far more than a seasoned, dry piece of wood. More common with staves than board bows however.
Your bow isn't bad at all, and heck you've made a bow! Always be proud and take what you've learned on to the next bow, and the next. We never stop learning! I hope you take my points as constructive criticism, and not just a dig at your work!
