actually, I'm 20, and a junior in Embry Riddle Aerospace University
Anyhow, I forgot to answer #2... basically, you want your cg at the center of your lift... so, if you have canards, and they have null lift (symmetrical airfoil) then you should be fine, and it SHOULD fly like any other airplane, with the cg based on the wing alone... The same is done for std tail aircraft, but the tail is usually null lift (sym airfoil) so its not a consideration... if the same is true for your canards, you're fine. So long as you remember that if you're pulling up with canards, you're increasing the lift on the front, not decreasing it in the back (as a normal plane works), so AOA comes into effect... which is what causes the canards to typically stall before the wing (typically, not always).
Best way is to glide test... which you can do with no equipment on the aircraft... if it flies empty (and you dont add too much weight) then it'll fly fully loaded. You could add balast to make sure it'll fly with the load... glide testing really is the best way, thats how Ive gotten all my models to fly
25% mac is a rule of thumb, you'll NEED to adjust from there depending on how heavy the nose/tail is...