do another 25% water change...... think it is abt time 2.
change ur testkits to other more reliable ones, e.g. salifert. sera has been reknown to be quite inaccurate amongst reefers' opinion here in src.
bio balls and rings how? remove them!!! if u hv existing LS in ur tank, and u r afraid that by removing all the bio balls and rings, ur system might not be able to take it, then remove it in stages. e.g. 1/4 this week, 1/4 2weeks later, so on and so forth. in the meantime, can invest in more LRs or hv a DSB for bio filtration.
upgrade to a better skimmer....... problem does not lie only wif the pump.
juz me 2 cents worth of advice.