I have a 99 f250 2wd with 248000 on it, It still runs but is weak. It is a work truck and has had a fair amount of pulling trailers. Anyways it needs a top end rebuild which is not uncommon for the amount of miles. You might check your compression ,a dry test then a wet test, the results will tell you how bad your rings are worn. You also might want to get ready and change out rubber hoses. If your engine is running weak id look into a rebuild.
I don't know about the guy that just posted, but I have a 1995 toyota tacoma 2.7 with 255,000 miles and it still runs like new, my mom has a 99 nissan altima with 210,000 and it still runs great. I also have a 2000 F150 with the 5.4 160,000 and it runs like brand new. Its all in how you take care of them. If you run the crap out of it constantly, then yes it probably will start giving out, but if you take care of it it will run forever. My dad had a 97 ford f150 with the 5.4 and it had 400,000 miles and it ran great. Just take care of them.
Yes
If the motor has been taken car of an serviced like it should be it should still be good
Yes, I believe any cars with over 100,000 miles is a lot. The engine with probably start to give about now.