Your report indicates an estimated NM of -16.4. Click on the call sign of WFXP and you see that the hill is rather close to the receive end of the path. These factors don't bode well for reliable reception even if you could find an antenna with gain in excess of 20 dBd. This qualifies as needing 'extreme measures'.
Here's an attempt at answering your questions;
If you can invent a losses combiner, you would hope to get twice the power. Expressed in decibels, that would be 3.01 dB additional gain (rounded to the closest 100th of a dB). Many folks have tried using a common two-way splitter in reverse... but it has at least 3.5 dB insertion loss, thus a net loss of gain.
Stacking horizontally versus vertically will not produce any more or less gain on average. In practice, chance may prove one better than the other... from moment to moment as multipath can affect one antenna differently than the other. Each antenna may not receive the same amount of power as the other, and a slight change in antenna location can produce a significant change in reception conditions.
You could use a low loss network made of two sections of 106Ω coax (you may need to build your own coax, I don't know of an RG-X type to specify). Each section of 106Ω coax would need to be 1/4 wave length long, which is 0.144 (electrical length in meters) at 521 MHz, the center frequency of CH-22. Presuming the velocity factor of the coax is less than 1.0, you would need to adjust length to match the coax used... multiply the electrical length by the velocity factor to obtain the physical length. The ends of the matching sections opposite the antenna ends would be joined together with the RG-6 down-lead.
If this seems a bit much... I think it is, at least for most folks. In the real-world instances that have used this type of combiner, the net gain is about 2 dB due to the losses that are lower but still present.
If you really want to try building something... consider a rhombic:
http://forum.tvfool.com/showthread.php?t=2865 This is a wire antenna, very big, roughly 30' to 40' long. But the up side is that if you can cut wire connect it together, you may have the skill set needed to build an antenna of this type.