Impactzone:
If I were you I would DISCONTINUE use of ALL topical drugs or creams, with the exception of washing your face gently with the Cetaphil twice a day... this is mild enough to keep your face clean, but not be irritating to the skin. The Clindamycin topical tends to have a base of alcohol (as do many skin preparations) which can actually irritate the skin when it's in a condition as you describe... Sarna can be irritating as well.
I would stick with the Cepahlexin 500mg 2-3 times a day which is a great antibiotic for the skin and will help clear up the pustules. If you use soft cloths wet with just cold water, this will also have a cool soothing effect. Obviously you want to make sure you change the cloths each time as to not have any additional germs exposed to that raw skin-- though the antibiotic you are taking should prevent this from happening. As tempting as it may be, I would try to refrain from squeezing on the pustules because this only causes more trauma.
IF you feel you need something additional to soothe the skin, aloe is a great choice for this. You can buy STRAIGHT ALOE... no other ingredients (as I said, many skin preps have an irritating base). If you have an aloe plant at home, this is the best way, break a piece of the plant off and squeeze the aloe right from the plant. OTHERWISE, just stick with what I suggested above.
If it doesn't get better, you may need a dosage adjustment, so stay in touch with your oncologist if it worsens.
Good Luck... I hope this helps.
Regards,
CancerDad