Even with a 50 foot antenna in sloper configuration (lowest point around 5 feet above ground level, highest point maybe 12 feet) NVIS and further distance propagation are both possible at modest power levels. Propagation conditions (read: luck and timing) also play big parts, so keep on experimenting - you'd be surprised what you can do with low power when the conditions are good.
I would recommend using a frequency closer to 6925 kHz if possible. The 6800-7000 kHz range is where many people with SDRs recording the entire band look at for activity. 6850-6975 is an even better range to shoot for (if possible). I know your rig is crystal controlled so if you have crystals for those frequencies they might get you better results in terms of listenership and reports. 6925 kHz is the "home channel" for 43 meters, followed by 6955 kHz. Just avoid using 6910 kHz and 6915 kHz as these frequencies are used by the U.S. Government for disaster relief operations and other emergency communications.