The problem with the iCal file seems to be in the VTIMEZONE section. The TZOFFSETFROM and TZOFFSETTO entries are the same for DAYLIGHT and STANDARD. Also, the RRULEs have the wrong start and end dates defined in them. I believe this explains the issue seeming to be related to daylight saving time. I changed the VTIMEZONE section to:
and changed the TZID in the VEVENTS to America/New_York.
My Google calendar is TZ is set to (GMT-6) Central Time. Works fine now. Total research time including testing 30 minutes. Hope this helps the 'developer'...
Users would have to tweak the generated file and manually update Google with it... not impossible, but it's a little snarly and VERY inconvenient.