You should also consider reading the NCERT of 11th for topics of IJSO that are taught in 11th and 12th. You can follow JEE books for the same.
Things like Gas Laws, Stoichiometry, Projectile, NLM are best covered from these books as they provide more depth (but they'll only benefit you at INJSO level, NSEJS has more trivial questions).
For maths, stick to NCERT of 11th if you want to do more (12th not needed) but your FIITJEE compendium for NSEJS would be sufficient.
I have no idea about Biology (I never tried studying it, find it boring :P). But till NSEJS 9th and 10th NCERT should suffice.