You’re fine to cheap out on a belt tensioner, just don’t cheap out on crucial items like timing belt kit.

In this case yes just pull the hub by unbolting but a charging a customer over $200 labor for once stud replacement is not right, this is not a safety issue one slightly grinded stud out of 5 is not going to cause a safety issue. I could care less that you are a certified Honda mechanic, the stealership has no problems ripping off customers.

It’s a time and money saver. You grind part of the round tip so you have enough room to work out the old one and install the new one. If you don’t know this trick then you probably don’t know what you’re talking about. On Hondas you have to press the hub bearing out which calls for 2 hours just to replace a stud a $5 stub, so this is a quick alternative and it’s effective.

It’s good if you felt it snap in there It’s good.

You’re fine even if it lost a quart which most probably didn’t lose that, engine will be okay. Just make sure they reimburse you for the filters.

Need to take it back to him and have him fix it at his expense.