Trying for KSNK, real CH-12 would call for an Antennacraft Y10713. As you have already concluded, the task is made more difficult given the powerful signal on CH-10 which limits you to using a preamplifier that has the ability to tolerate strong input levels. You could try an RCA TVPRAMP1R though I think you'll find it to be at the edge of overloading. I've used a Channel Master CM-3410 + PCTMPI1G power inserter in this sort of situation, you also need to use a weather proof enclosure on the mast to protect the amplifier unit. In the end, you need some good fortune to pull this off.
If the single Y10713 and preamp failed, I would also consider a stacked pair of Y10713's as a 'back-up' plan. This would certainly be an experimental project.
http://forum.tvfool.com/showthread.php?t=1024 I might contact tinllee.com and ask their opinion about a preselector filter also.
The two UHF signals should be an easy 'get'. I'd use a DB2e... Though the DB4e would not be overkill.
