No way to avoid overnights if you want the AF MIA-PTP flight and are going to/from ATL (due to flight timing) unless you book separate positioning flights to/from MIA on another carrier (such as AA. NK also has late night MIA-ATL flight if you are desperate). There are no MCO-PTP flights currently showing in schedule. Flying to/from MCO will still involve an MIA connection and overnight stay on outbound (return connection is same day possible as MIA-MCO filght departs at 9PM).

Roundtrip DL Main fares on MIA-PTP start at $550, AF has slightly cheaper Light fares starting at $510 roundtrip. DL Main fares on MCO-PTP start at $445 roundtrip which looks to be about as cheap as it gets for DL fares to PTP. BOS and JAX are slightly more at $463 RT and would also be considerably more inconvenient. ATL-PTP DL Main fares start at $845 RT. Cheapest option will probably be separate positioning ticket to MCO combined with MCO-PTP roundtrip ticket. But you won't be able to get around having to overnight somewhere to/from ATL if you want to stick with all DL flights. Note that the ULCCs like NK and F9 haven't extended their schedules out to next Winter/Spring yet.