2010 Prius coolant level not moving but rattles on cold start??

I know nothing about cars really... but I used to work at a Toyota dealership and know a lot about techinicians and their temperament.....

My 2010 Prius (with 182k miles I have owned since 2017 when it had 70k) has never had any issues until I noticed the common cold start rattle a month ago. I immediately took it to the dealer after the check engine light came on a day or so later.

THE SHORT OF IT:
The toyota mechanic there knew it was the head gasket before he looked at it...... which was a little offputting. They had it for about an hour and stated that it was indeed the head gasket and it had "misfire codes."

THE LONG OF IT:
Here are the suggested repairs and reasoning as well as my observations:

1) Toyota Tech report says: "misfire codes, coolant low, possible headgasket leaking." And the tech advised me to replace the motor and not bother with the head gasket.

My thoughts: I have never had the car overheat and I have been driving for a month since then at speeds up to 90 and distances up to 100 miles round trip (and up steep highways at 86mph average on my commute to work every Thursday only). I have been religiously checking the coolant level and there is no coolant level drop in the reservoir....not even a bit since then. The cold start rattle is sporadic and only does it occasionaly first thing in the morning. I have noticed that if I turn it on put it in reverse to back out of my garage, before the engine kicks on, the rattle almost never happens.....while if I do not put it in reverse right away it happens half the time. The check engine light will go away and then come back but has been on for the last couple days. I feel lik ethe tech half assed the diagnostics but I don't know if I should doubt the bad news since I am no expert at this and the online research I have done is jus confusing me more.

2) The Toyota Tech also stated that the "ABS light was on" and it probably needs a brake actuator and pump but he needed another $140 if I wanted it diagnosed.

My Thoughts: The weird thing there is I have never seen that light on and he also mentioned, before looking at the car that this was a "common problem my car likely had." I feel like he is making assumptions about some pretty expensive repairs without doing the real due dilligence. Again, I may just have wishful thinking and he coul dbe 100% right but my gut is telling me they didn't try hard at diagnostics on my car.

When I cam to pick up my car they had these reccomedation options:
1) Replace the Head Gasket for $3,516......the tech said I shouldnt do this as it was risky and the car may need a motor anyway and this money would be wasted.
2) Replace with a used engine with 101,000 miles on it for $7,468.....this was what they wanted me to do or they advised to tarde it in on a new car since mine was essentially worthless now. They also said the reason to get rid of the car was that the Brake Actuator would likely fail soon and that would be another $2,800....bringing my grand total to save this car to about $10,200.

I amnot sure what to do! Here are my options I am mulling if anyone can give me their two cents please....

1) Should I try the head gasket?
- It sounds to me like this is risky and I may just be throwing $3500 away on a gamble
2) Replace the motor?
-I would want to look for a motor with less than 101k on it as that seems awfully high to me and not worth the risk either. Surely, there are motors for similar cost with less miles? I am not sure though and if thebrake actuator is really going out, then that would suck to get hit witha nother huge bill soon.
3) Ride it out for as long as I can and pray used car prices drop?
- Since the motor needs to be replaced anyway and I have towing on my insurance (and I wont go further than 50 miles away from home) why not just ride it out and keep an eye on the coolant for the next few months?
4) Go out and get a used Prius and let this one sit until I decide what to do with it?
- I do not want to pay these crazy prices for used cars but my credit is good and I have the budget for a car payment now if I have to.

Thanks for any and all advice on this verbose thread.

***I dont think the tech was being dishonest (didn't get that vibe at all) but I do think he was being lazy and quick to jump to his biased assumptions.....I could be wrong.