Really quick suggestions:
#1 - A 2 meter mobile rig for each of you will most likely give you the 20-mile comms (communications). A 2 meter handheld would work in the woods to talk back to the vehicle. A mobile rig new <$300, used <$200. HH (handheld) new <$200, used <$100
#2 - A multi-band HF rig with appropriate antenna system. This will give you the ability to talk regionally, state-wide, nationally, and world-wide under the right conditions. Most of the modern rigs are solid-state and operate off 12 vdc. You can use this in vehicle or base with the right power supply.
#3 - Solar power system for the rigs can be put together fairly easy. The determining factor for the size of the system would be how much you will tx (takes more power from the batteries). All the equipment in my shack is solar powered.
#4 - Technician is basically a beginner's level. It limits the frequencies you can use and the type of transmissions you can use. It is mostly for local comms unless you are using Morse Code. General is the next level and gives you almost all the privileges of Amateur Radio. It allows you to use all the bands and modes, but it limits a few small sections that are reserved for Extra. Extra Class gives you total access to all the frequencies and modes available. It is the highest level license, which requires the most difficult exam.
#5 - You're welcome.
#6 - Yes, you can have your entire radio setup operating from solar power.