Chip antenna mounting considerations
It's probably a tuning loop or another structure that makes the small chip antenna act "slower" than it really is (i.e. forces it to operate in the 868MHz mode rather than a faster mode). Dropping it will almost certainly compromise it's operation but the only way to measure by how much is with a VNA. Unfortunately this is the common trade-off; lower frequencies make antennas with larger physical features. 

Re: 50 Ohm trace and 115mil thickness. Yes, this is correct for a 2 layer 1.6mm FR4 board. And yes, its very wide. I use a 4-layer board on my M12. Typically the thickness between layers 1-2 and 3-4 are close together (approx. 8.26 mil) while 2-3 are far apart (maybe 40 mil). Check the stackup with your pcb manufacture. Anyway, with a smaller thickness you should start to see more reasonable 50 Ohm trace widths.