[lbarger]

1) There are calculators available on-line for simple chain configurations. i.e. between two sprockets. If those sprockets are the same size, you only need to space the axels in 1/4" increments for #25 chain. If you use a half-link you could work on 1/8" centers. However, to drive 3 wheels from a single chain is significantly more complicated and may require the use of CAD for your specific configuration.
2) Obviously, the more wrap you use on a sprocket, the less likely it is the chain will be able to jump. The general rule of thumb I use is 120 degrees of wrap, but geometry does not always allow that. With reduce load on the chain you can use less wrap on each sprocket, but I caution against going with less than 90 degrees of chain wrap.
3) I've always used master links. When properly installed I have never had an issue with them. Simply need to make sure the retaining clip is properly engages with the grooves on the posts.
4) #25 chain can no handle the loads that a #35 chain can. You need to make sure you do not over load the chain and cause it to yield/stretch/fail. As with any chain proper alignment of sprockets is critical for keeping chains on sprockets. My experience is that #25 tends to 'relax' or stretch more than #35 chain after some use. I attribute this to the greater number of links for a given length and wear at each of those links. Keep loads reasonable should help with this. Fortunately this year's game should not involve a lot of pushing so managing your chain loads should be fairly straight forward.