robsouth and jhilley, thanks for the links. Yup, these look like just what I need.
1. Valve2. ValveWell, live and learn. I got a bit impatient and tried to install two one-way 1/2" ball PEX-type valves about 4 or 5 feet upstream from the freshwater tank instead of ordering one of the above valves. One valve would turn-off flow from the freshwater tank, and the other valve would open up the hose to allow flow from the anti-freeze jug to the pump. The hose running from the freshwater tank to the pump on my TT is clear, flexible, reinforced hose with a 1/2" inside diameter. I used all 1/2" PEX valves and adapters, so there shouldn't have been any restrictions to flow. Once I got everything connected, I turned on the pump and noticed that pressure at the faucets was only good for about 4 or 5 seconds before the pressure would drop about 50%. Bypassed my PEX installation (with a 1/2" inline coupler) and everything went back to normal. For some crazy reason having a "T" connection extending 4-5 inches off the main hose caused some kind of turbulence which reduced flow to the pump.
Well, all was not lost. After I pulled out my failed 1/2" PEX valve installation, a flash came to me. All I had to do to winterize was drop the pump side of the 1/2" hose I had just cut into a gallon jug of RV antifreeze. Once I had good antifreeze flow throughout my TT, simply "plug" both the hose end that goes to the pump, and the hose end that goes to the freshwater tank. When spring rolls around all I gotta do is remove the plugs and reconnect the hose to/from the pump and freshwater tank with the 1/2" inline coupler.
I still may install one of the above 2-way valves, but for now this seems like an easy enough solution for getting antifreeze directly into my pump as close to the freshwater tank as possible.