Yes I concur it must indeed be the propagation but I've never heard it quite as extreme as that before. I used to get something similar when I had my own HF set-up some decades ago, although not as extreme. I actually found your post in the 'set-ups' forum showing your equipment and antenna and I originally started out with a similar whip antenna myself. I am in the UK and had no problem picking up Shanwick and Stockholm (also Berne radio and Portishead radio then too) but Gander, NYC and Maria would all be hard work unless at night time. This was with a Sony ICF2001D too, which was quite well known for its good filters over other cheaper sets.
I did some experimenting and bought one of those long wire antenna kits and basically bolted it to my upstairs window frame, extended it across my 25ft garden and bolted it to the shed at the other end. The difference was phenomenal and I had no problems picking up 11300, 5658, 8942 (Singapore) and the Caribbean (8846) on an evening, which are all some distance from the UK. The only problem was that it picked up a lot more noise as well but the signals were strong enough for it not to be too much of a concern. Some time later, upon the advice of an HF 'expert', I changed to a horizontol wire loop and that cut out quite a chunk of the noise and I continued with that set-up til I had to move and no longer had the space for it.
I mention all this because as a fellow HF fan yourself (of 30yrs!) you might be interested in ways to improve your 'reach', and as you seemingly have a lot of (low noise) space to play with there in your wooded area, it may be something to look into perhaps. You would be amazed at the difference a loop - or even normal long wire - would make. The HF freqs certainly prefer these kind of set-ups over discones and whips.
As far as adding/changing the freqs on the feed goes, I would ask that it remains as is please. 11330 has all the same traffic as 6577 so you wouldn't actually be achieving anything. Assuming normal daytime hours, flights from say NYC down to the Caribbean islands always start on 6577 until roughly Bermuda latitude, and then they are changed over to 11330 for the remainder of the flight, and vice-versa when they are coming north. 6577 has more traffic overall as that has the flights to and from Bermuda which generally come from the north/east direction and not up from the islands. 8918 is the other 'main' frequency in use through the day and that covers the traffic on the L451 and L452 routes that run SE/NW in the bottom left corner of the WATRS oceanic area. L451 is JAINS > LETON and L452 is OXANA > GALVN > LNHOM.
The transmitter for the top half of the oceanic area faces SE from Long Island and covers 3455 5550 6577 and 8846. The transmitter for the bottom half faces SSE and covers 2887 5520 6586 8918 11330 13297. There is a 17 and 21 meg freq as well, but I've never known conditions to be that bad where they are used.
In terms of frequency usage, from my regular listening to that area you won't go far wrong with these :
2887 - very very rarely heard
3455 - 2100/2200z-0900/1000z
5520 - not used much but only during hours of darkness
5550 - 0900/1000z-1200/1300z and sometimes for a short period in the evenings before 3455 becomes primary
6577 - 1200/1300z-2000z/2100z every day
6586 - 2000/2100z-1200z virtually every night but 5520 sometimes used instead
8846 - only used if there's too much traffic for 6577 to handle. Sat/Sun afternoons is usually the only time it is used
8918 - 1200-2100z daytime primary for all traffic on the L451/2 routes
11330 - 1200-2000z daytime primary for the southern half of the WATRS oceanic area
13297 - rarely used but sometimes used as an overspill for 11330 on Sat/Suns
6577 is certainly by far the 'best' frequency of the bunch!
Hope you find some bits useful and thanks for providing the 24hr feed!
PS. I have PM'd you on a separate issue.