On the 260/280 topic. Bisulfite conversion does not only make your DNA single stranded, but also degrades the DNA. This results in many small fragments with an -OH group at the end, which will thus "pollute" your spectro profile in the range of the ethanol group, so that you 260/280 is no longer 'clean' .
@ people doing double stranded DNA quantification after bisulfite conversion: do a single stranded method and your yield will be better :-). Bisulfite conversion yields non-complementary DNA strands.