To identify a rhetorical form, examine what the addition accomplishes. «غير مفسدها» removes an unwanted implication of destructive rain, so it is ihtiras. «على حبه» raises the merit of giving, so it is takmil.
Likewise, «إن الباطل كان زهوقًا» is an independent sentence strengthening what precedes, a tadhyil. «كأنه علم في رأسه نار» supplies an emphatic image at the close, an ighal.
An expression may have more than one rhetorical dimension, but identifying the particular device under discussion requires explaining the actual effect, not merely recalling its name.