I know that feeling. I have had 1 car and 1 truck that I bought new, (2002 Altima and a 1995 S-10), and a 1970 340 Dodge Dart Swinger that I worried about every moment of break-in and if I had done anything to hurt them or shorten their life expectancy. I still regret parting with them.
To answer your question, you are fine. The stock temperature gauge is not very accurate in any vehicle. If it is near operating temperature, what you did was fine. I do not know if you just got the car, sounds like you did, and found a sweet low mileage example. You want to do everything right to make it last.
If you had been in near zero temperatures, just started the car and did a burnout. Then you might have shortened the lifespan. Since you were on the road, I am guessing not only was the motor warmed up but the other fluids such as; tranny, differential, etc. Were up to temp. As well. You only accelerated from a rolling speed. The downshift you fealt was just that, a downshift. When you press the gas far enough a cable called the, "kickdown" cable, downshifts the car a gear to help the car stay in the power of its' RPM range.
Let me knkow what other questions you have and I will look to answer the other posts you mentioned if they have not been replied to. I can also give you a general guide to my philosophy on car maintenace, do's and dont's of operating a vehicle to increase its lifespan and other stuff I have leraned along the way such as brands of fluids, chemicals, etc. These are my own philosophies, so take what you will if you want to hear them and make your own.
I totally understand your situation and the way you feel. I am currently finishing a project that I will dub my new, "baby". It's a 1990 Acura Integra with a 1998 JDM Integra GSR drivetrain and OBD-1 TYPE-R JDM ECU.
If there is anything else I can answer let me know.
If you want to know my car philosophies, let me know the cars' history, e.G. How many previous owners, how long you have had it, etc.
Thursday, October 7th, 2010 AT 6:49 PM