The problems were worse on Linux, and so I gave up and loaded instead Windows.
But I generally remained unhappy.
Well, I finally bit the bullet and fixed the problems:
First, I replaced the trackpad with the (much better) one from the newer T450s, and upgraded the SSD. This step was a mild PITA, but I got it done.
Then I replaced the wireless card with an Intel one.
Finally, I installed Linux (Mint).
MUCH better; like a new computer!