2005 Mercury Montego Not starting, need advise.

I was on the highway when the charging system/check engine/battery/ABS lights & notifications came on, then minutes later all if the dash lights go off. Had car towed to local Midas thinking the alternator needed to be replaced. At Midas, they tried to start car, put a new battery in and said the starter tries to turn over but factory alarm is going off now and they said they can't get it to shut off so they can't test alternator to see if that's the problem. A friend who has a car alarm installation business went to Midas to disengage factory alarm, made sure both keys were working, so we think we've eliminated the alarm issue but had to have it towed to another shop that specializes in car electrical/computer issues.
Here's a little more information that may or may not be associated: About a month ago, my drivers side HID headlight went out and there's a lot of condensation that doesn't dissipate which likely caused the headlight failure. It has been raining for a few days so I'm wondering if something electrical got wet?
Any suggestions, thoughts, or ideas would be appreciated? What do I try now? Alarm, Alternator, Wiring issue or computer issue. Please advise?