The three packets, along with the rest of the money, stay together in the bag for the duration of the trip down the Columbia to Tena Bar. Upon reaching Tena Bar, the bag opens, some of the money spills out. The three packets end up together on the sand while the rest washes away. Not that far fetched. Nature is chaotic and doesn’t always follow specific patterns - particularly debris in a flood water.
Regarding the jump time, to be fair, your theory requires moving the accepted flight path several miles west. The exact time that Cooper jumped is far more questionable than the flight path.
For example:
8:05 was the last time the flight crew hear from Cooper when he responded to them on the intercom that "everything was OK"
8:10 was the first time there are any reports of "oscillations" (FBI Vault, Part 41, p. 31 & 32)
8:12 was the last time there are any reports of "oscillations".(FBI Vault, Part 41, p. 31 & 32) At this point the plane was just east of LaCenter.
There is no official report of a "pressure bump" which is generally used as the point at which Cooper jumped causing the stairs to swing back up. We don't know when that took place, but we know it took place AFTER 8:12 because the oscillations preceded the pressure bump.
So, while we don't have an exact time of the pressure bump, we do have pilot statements. Rat said initially that the pressure bump was felt 5 to 10 minutes after last contact (8:05). That would put the bump between 8:10 and 8:15. We know it can't be between 8:10 and 8:12 because that is when the oscillations are happening. So it would have to happen between 8:13 and 8:15. However, Rat later told Carr that the pressure bump occurred 10 to 15 minutes after last contact (8:05). This would give you a range between 8:15 and 8:20 for the pressure bump.
However, further statements by the crew were that the pressure bump occurred when "the lights of the suburbs of Portland were visible" but they "had not yet crossed the Columbia. The plane crossed over the Columbia at 8:17, so we can eliminate any bump happening after 8:17.
Thus, the timing of the oscillations combined with the statements of the pilot give a range between 8:13 and 8:17 for Cooper jumping and causing the pressure bump. The median of this time range is 8:15. At 8:15 the plane is over the Orchards area.
In actuality, the northernmost jump point IS just north of Battleground and the southernmost would be the northern banks of the Columbia. I used Orchards as a center between the two.
My contention is that the jump occurred in the 8:16/8:17 time frame and Cooper and/or the money came to rest very near the banks of the Columbia.
As far as what happened to Cooper and the money once it left the aircraft is merely an educated guess, but I believe the river is the most likely vehicle for the money to end up on Tena Bar.