In an accident Friday night and it’s a holiday weekend… Never had this happen to me so I have some general (?) questions while I wait for first contact.

As stated, I was rear ended by a car going full speed while I was stopped at a red light Friday night which also pushed my car into the car in front of me, called the insurance company, filed a claim, all that's been done, but while I wait I have a couple questions:

1)car behind me is obviously a total loss, the whole front end was smashed to the cabin, the car in front of me received cosmetic damage and just needs the plastic fender replaced as the police ripped it off to ensure nothing dragged and both the driver and myself both questioned because it literally only cracked a side of the fender… Mine on the other hand, based on speed and impact, possibly caused frame damage but feels more in the "will they, won't they" area as to whether it will be a total loss, does the mechanic/shop decide if it's a total loss or does the adjuster?

2) Obviously, the person who slammed into me is at fault for my vehicle, but what about the vehicle in front of me? I know that while driving, if your pushed into another vehicle, you can be at fault for not leaving a safe distance between you and the next vehicle, but does this still apply when stopped at a red light? (I mean, you can't be leaving a car distance space between each car at a red light, that would make traffic worse and cause other issues)

3) It's a holiday weekend, (MLK Day is Monday), should I still be waiting by my phone expecting a call from the assigned adjuster before Tuesday? (Do adjusters work weekends? Holidays?)

4) Car was towed to a local place by the county police, am I able to go get some missed belongings out of the car before the adjuster assessed the vehicle?

5) the vehicle that hit me is on one form of USAA (USAA General indemnity co) while I'm on USAA (casualty insurance company), hopefully that should make communications easier, but the car ahead of me is Progressive (haven't had a bad experience with them in the past, so fingers crossed), will all 3 insurance companies need to interact with each other if the vehicle behind me is found at total fault for both? (I.e. ins1 (aggressor) does all talking to ins2 and ins3, or does my insurance company need to talk to both and then the car in front of me has to talk to both, etc?)

6)it was my vehicle, my insurance policy, but my partner (listed as an authorized driver in my insurance) was behind the wheel with me in the passenger seat, when called for interviews, are they able to deal only with me or do they need to speak to him? (This is his 3nd accident where someone else was at fault in the past 2 years, hell, the anniversary of the last accident which was terrifying for both of us is coming up in 3 weeks, so his anxiety is through the roof, his therapist is on vacation, if I can limit the additional stressors and anxiety triggers, I would prefer to try)

Sorry, it's a lot of questions, but I just bought this car in October, paid it off in November, haven't even gotten it's first oil change…. Feeling a lot of things about this incident and even just posing these questions somewhere is easing my mind a little bit . Any info appreciated and if I'm told "no one can tell you but the adjustor", I understand.