Okay, so you have 19.44 VAC power on terminals 1 & 2. The keypad is powered from terminals 4 & 5, and I'd normally expect to see ~12.5-13.5 VDC there, depending on the load drawn by peripheral devices, including keypad(s). What are you reading at Terminals 4 & 5?
Also, what's the status of your Control Panel's (the Safewatch Pro's) backup battery? It should normally read ~13.5 VDC in standby (not in alarm) mode.
Anyway, if you're reading ~13.5VDC on terminals 4 & 5, and zero at the red and black on your keypad, then it's probably a wiring problem between Control Panel and Keypad, not unusual after a lightning strike, i.e., a wire blown open.
If you're reading zero voltage at T4&T5, then power take the KP wires off and measure T4 & T5 again, to see if the KP is shorting power from the Panel.
WARNING: Before reconnecting Keypad, power down the Panel (unplug transformer and take one wire off battery) . NEVER connect live power to a keypad. For some reason it's prone to zap them. Connect the KP(s), whether at Terminals 4 & 5, or at the KP itself, and only then power up the Panel.
Please let us know what you find.
EDIT: If you need to replace your keypad, I'd recommend buying a Honeywell 6160, or at least a 6150, rather the exact model of your old keypad. Your Safewatch Pro 2000 was a slightly modified Ademco/Honeywell Vista-20SE, at least 13 years old, but Ademco/Honeywell makes its panels and keypads back-and-cross compatible. If you currently have a 6139, 6128, 6148 or other, it's going to have to be replaced within a few years at best: Keypads have moving parts (the keys/contacts) that wear out.
SECOND EDIT: It's late and I've had a hard day, or I'd have thought of this earlier. I forgot you're going to have to program your new Control Panel, so you either have a 6139 (Alphanumeric) Keypad, or you're going to have to get a 6160 KP anyway. Don't attempt to program without an Alphanumeric Keypad (6139 or 6160). If you have your original KP, it's due for replacement anyway. Any 6139 on ebay is at least 13 years old, and keypads have moving parts that wear out. I strongly recommend buying a 6160 to replace whatever you have. Ademco/Honeywell made their panels & keypads back-and-cross compatible, so newer KPs are compatible with older Panels.
Let's get power to your keypad and see if it needs replacement before we can proceed.