Have you seen the mfgc or rsp? They may help you get a more consistent experience with your reader
xSeries implants are unfortunately prone to difficulty coupling due to their antenna size/shape. You may wish to consider a flex implant, which would likely improve range as well. An xSeries is usually workable, but flexies may be a little more convenient
I highly recommend spending some time with the xFD that came with your implant to try to find the best sweet spot on your reader, that’s where you want to put the implant, it does take some practice. Usually you’ll want to put your implant perpendicular to the antenna of your reader, if possible
It may also help to share what NFC reader you’re using, as some forum members may have experience and specific tips for it
Probably the car’s reader would use the UID of the tag, and the data sharing would use NDEF records, so there wouldn’t be any conflict there.
You can put multiple sets of data in the form of multiple ndef records, for instance, if you wanted to store multiple links on your implant. If you go this route, be aware that usually only the first NDEF record will automatically launch when you scan a tag with a phone, you’ll need an NFC app to see the rest
If you can share more about what data you want to share, and any other uses you may have, we may be able to give more specific advise
Almost certainly impossible to clone your key fob to your xNT, though depending on the chip type you may be able to clone it to a different implant. If you can scan it with your phone or another tool to find out what chip it is, or share photos/brand identification/other info about the fob, we may be able to start you down the right path there too