How many times can you extend NM-B with splices/junction boxes?
From what you are proposing, you are only lengthening the run by 10 feet. Your circuit is still only 85 feet long.

Short answer: Unless you are really loading this circuit heavily (~16 or more amps) you will be fine. There is no limit to the number of boxes or splices, only a length limit.

In the specifications of most of the commercial and industrial jobs we wire they require an increase in branch circuit wire size if we exceed 100 feet. This is a "rule of thumb" without doing a voltage drop calculation.

The definitive answer comes with that voltage drop calculation. There are many web sites online where you can enter your particular information and get a voltage drop estimate.

Also, If you are running PVC you don't need the UF cable you can use THWN rated wire. If you just want to protect the UF it only needs the PVC where it is exposed as long as you bury the UF to the depth required by the Code.

Good luck and stay safe!