If all events are a single line, it would be significantly more efficient to do this:
SHOULD_LINEMERGE = false
Also, your settings are the default, so you shouldn't need them anyway. Is it possible that Splunk is not interpreting the timestamp correctly? If Splunk doesn't recognize the timestamp, then your BREAK_ONLY_BEFORE_DATE = true setting will not work.
my_custom should be the name of the sourcetype of the data - it must match exactly, including case.