Your items 1 & 2 are nonsense. You only need address item 3.
I think the simplest approach is to use PLX-DAQ, which easily adapted for use with Arduino. It is an Excel macro and therefore enables you to enter data direct into Excel - on screen and in real time. All you need to do is format the output with comma separation as you would for any export in CSV. No need for a clock, date and time stamping is done at the PC end. PLX-DAQ can also be used to display real time graphs.
You can also send the identical material to to a terminal programme like RealTerm, which saves it to CSV for ultimate transfer to Excel. Again, the clockstamp can be done at the receiving end. I don't know how either of the above can be used long term but broken into short term files. They probably can but I use an on-board SD card instead, and change the file name daily. Needless to say, this procedure does require an on-board clock.