Maybe it doesn't fit your needs but I saw AC Rouge at TXL last week and I saw publicity of a direct service to Toronto.
LOT business is OK and so are the lounges at WAW, they don't get any more crowded than others can.
I would fly directly to Germany and would suggest you look at Deutsche Bahn for the journey from your arrival point to Berlin. There is a station in Frankfurt Airport where many long distance trains stop, Munich is a bit more hassle and you need to go into town. DB in second class is pretty good especially on the ICE trains and few pay for first on DB with their own money.
https://www.bahn.com/en/view/index.shtml
Berlin is a great city to visit so do make the most of it.