I've bought XPS 13 around the same time also maxed out everything and can relate to 90% of your issues. I've also had firmware updates that rendered the laptop completely inoperable (a technician needed to replaced the board).

Unfortunately the level of service also dropped significantly. When I bought XPS 12 6 years ago it was stellar making me a loyal customer but now... some things can be blamed on Intel (broken Thunderbolt, and the TB15 fiasco) but not all...