I've a few questions and concerns about prepare weapon and iwd

Please point out any faults in my synopsis.
First, the # of slots on your weapon is determined by the amount of diamonds. The number of slots is the square root of the amount of diamonds you have?
To prepare a weapon, first say /mark weaponname. Second, you put the diamonds (100) on the ground in front of you. Read the prepare weapon scroll, and your weapon should be come like so 'Knumb's Inferno Sword of _____ (Improved 0/10)'.
On to IWD's. With my 10 physique, I can handle 7 improvements, though my weapon has 10 slots. I can use 7 IWD (By simply marking the weapon and reading them) until I level more in physique.
At any time will I grow too powerful for the weapon, and if so, what level/phys is that?