Love the TSportline.My prior ride is a 2008 Acura RDX with Nokian WRG4's and they seem similar but the SH-AWD seems more conservative with its limits.
According to TireRack, an 18"x8 rim and Blizzak 245/55R18 package will work on the Model Y. I tried to order it but the Blizzaks were not available in my area apparently.
Sorry to hear you are having issues. I did get mine through
Les Schwab Tires -
18x8 5-4.5 Black Rhino Boxer and
235/55R - 18 Blizzak DM-V2.
Looks great! Re "18x8 5-4.5 Black Rhino Boxer", are you sure your rims are 18x8 and not 18x8.5? Either way, I wonder if these would work on the performance upgrade Y?
How deep was the snow and was it wet?