"nk" terminology refer to horizontal resolutions so "2k" refers to a resolution of 1920x1080, aka "Full HD". If your monitor is "2k", 1080p will be the best you can get. 2560x1440/1440p is "2.5k"...
You've activated WEG boot parameter -cdfon but I see no enable-hdmi20 property injection in your Clover config. I would suggest you add that, I believe it's expected. If 1440p resolution remains natively unsupported/unavailable, try SwitchResX app.