You had the 30 day gap right, but the start date is different.
On-property guests start booking fastpasses at 60 days + length of ticket up to 10 days. Off-property guests book at 30 days, with no length of ticket bonus.
What's different between booking FPs and ADRs is that ADRs is 180 days + length of stay (also up to 10 days), while fastpasses is 60 days + length of ticket. So in the case of ADRs, a split stay does affect the dining later in the trip. Fastpasses are not affected by a split stay.
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