As you have been told many times by some very experienced people, including the editor-in-chief of What Hifi (who would expect to know about these things seeing as it is his job to know about them), your speakers are too big for your listening area and you are sitting too close to them, never mind the positioning & room shape problems you have. Cerwin Vega! are good speakers in large rooms (where they have room to "breathe") when cranked up, but they are not the right speaker for your room. you might be able to tweak the sound to some extent, but you will never get them sounding their best in your room. Sorry if that isn't what you want to hear, but there you go.
I honestly would sell them & buy a smaller speaker, designed for a small room. Additionally I would buy some stands to mount them on. You will be able to place them further away from the walls & corners which will help a lot. Look at speakers with a front firing bass port which will help reduce the detrimental effect that the sloping wall has. There are loads out there so your best bet is to find out from here what speakers would be good for you & then go & see if you can listen to them somewhere.