I don't know about 15 degrees 20 maybe and 25 is what is recommended by oregon for the 3/8 chain. From what it sounds like you are probably close to being right on the money with sharpening if the wood has a little grit to it. When you sharpen you chain at each fill up I assume it only takes you a stroke or two with the file to get the teeth right back correct? Semi-chisel may be most appopriate for what you are doing right now. As far a kick-back, most safety chains seem to lean toward the semi chisel cutter so I would have to assume that it is less likely to kickback. Although relying on the safety factor of a chain is akin to relying on a safety on a gun. Bad bad bad practice. The technique should be the safety device.
You could also bring a couple of sharp loops with you, I noticed both of your saw use a 20 bar, its fast to change out and you can sharpen in a controlled enviroment or at least a vice
For what it is worth I only use chisel chain, and I don't mind touching it up when it needs it, it doesn't take long to sharpen if it only needs a light touch.
Buck