Thanks for help guys. It suddenly started to work after I generated spritefonts again. Maybe there was some generation glitch.
So to wrap up I use spritefont generator mentioned above, and it works great, fonts are very sharp on mobile no matter how much I resize them (using scale).
ps. Fonts are very sharp only on mobile, in C2 preview mode they are blured - but that is not my concern now, just mentioning.