My downstream levels are currently at 13.6 dBm and SNR of about 37. I have the line of the low loss (-3.5db) leg of the splitter. Should I move the cable to the (-7.5db) in order to get the dignal down?
You signal level should be between -10 and +10 to be in spec so do what you suggested and see what your levels are. You might want to do that and then throw in a 3db attenuator prior to the split to boot.