1. plenty of people talk bad about PEX (Patriot Exalibur), but once you take some time to get familiar with the program and set up your defaults properly (as a scheduler), it's actually a great aid to scheduling. Yes there are some things that could be better, such as when it notifies you there is a conflight, it should pop up with the conflict instead of telling you there is one, so you don't have to navigate away from the page you're on just to see what the conflict is and if it's ok for it to be there.
You can set it up to automatically add 12 hrs of crew rest prior to a flight; you can check people's currencies, and in fact filters by grounding currencies to see who should be the priority for a particular event. It's a great SA-building tool. At my previous base, MX was also doing things in PEX, like pulling up the schedule on their own, which made the pen and ink meetings go a lot faster, and plugging in tail numbers against lines.
My current unit actually put the whole FHP in PEX, which my previous unit never did. Both use PEX for all Stan/Eval functions. There's a nice Go/No-Go display in PEX with green or red dots, so instead of having to look down a printed sheet from ARMS to figure out what someone is red for, you just click on the red dot and it tells you that person is overdue an instrument approach, or is missing a date for water survival training, or they still need to sign off FCIF 09-03B.
Then on the other side of the house, those who are not schedulers can login to PEX and easily see what they are scheduled for, can input commitments they have upcoming (outside of 2 weeks is our rule) such as medical appts or TDYs or Leave. "If it's not in PEX, it doesn't exist" is our motto for commitments and appts. It makes accountability a breeze. You can see with a few clicks of a mouse, who should be here and who shouldn't.
Jokes about Skynet aside, PEX is a great tool, just like all things, you have to actually take the time and/or get sent TDY to the week-long training at Eglin to use it to its full potential.
2. There's talk of bring PEX online downrange, but currently there are compatibility issues with currency information managed by ARMS on NIPR and the inherent classified nature of the ATO being on SIPR. In my community, we fly hard crews, who sit alert for multiple days at a time, so PEX isn't really needed for that. Different for a fighter squadron, though.
3. Haven't run across any so far. Having a backup server and database of PEX information is probably a good idea, but unless the folks running your PEX on base are complete morons, that's already being done.