I see you, Delco Bobby stated in your original posting that you have a 2050, but then later state several times it is a 2250. I'm presuming you have a 2250 SLEC, right?
Our low point drains are located just aft of the entry door on the passenger side:
In your images, you found the low point drains by looking through the hatch for your propane tank. Our 2016 model has the propane tank on the drivers side rather than the passenger side; we have a storage compartment just aft of the entry door.
For the fresh water tank drain and the plumbing in that area, looks like you can remove the bulk of the spray-in foam on & around the piping - they sure put a lot of it in these areas! Here's an image of mine:
The blue like at the upper right comes from the FW tank. The first intersection is a tee, then an ell to the valve. This is the fresh water tank drain, and as you found, it drains through the floor.
The tee connects to a two-way valve that does the following:
1) In the normal position in line with the blue & white nylon braid hose, the pump pulls water from the fresh water tank.
2) In the winterizing position, the handle points to the white nylon braid hose heading away from the valve in this image.
When the valve is in the winterizing position, you can unroll the hose and place the end into a bottle of pink stuff. Turn on the pump - it'll draw from this source.
To access this area from above, you can open the bed. I found out quite by accident that I could do this - I was digging around the converter/charger when I noticed a piano hinge on the underside of the foot of the bed:
Run the slide all the way out (Hint: To keep the slide motors in sync, run the slide out until it stops - hold the switch for one to two more seconds, this sets the stop points in the slide controller), remove the top mattress, and lift the bottom section up:
At the far right side, you can see down into the same cavity you were looking into from the access port in the rear compartment:
Now you can see where the lines go... The white nylon braid line at the top right side of this image heads from the winterizing valve to the inlet of the water pump.
This image shows the coiled line again that is the pickup for the winterizing solution:
To access the water heater in order to bypass it for winterizing, initially I removed the four screws holding the panel in place. This is located under the wardrobe/pantry, between the bed and rear dinette seat. However, I found an easier way - simply open the bottom drawer all the way:
To bypass the water heater, turn off both the top and bottom valves, then turn on the center one:
From the outside, remove the nylon plug, and step aside. To speed up the process, hold open the popoff valve lever. (I can post pics of that if anyone would like to see that process).
From this space, you can see the water pump:
The white nylon braid line from the earlier pics is the input to the water pump:
I chose to do both the compressed air and pink stuff methods to winterize. I found some lines that had droops, and some that were past points where water would sit unless I used the compressed air to remove the most of it.
The process I used:
1) Park the MH where the unit was leaning to drivers side & nose was pointing slightly down hill.
2) Open the access hatch in the rear driver side compartment, open the drain valve.
3) Access the water heater from the outside - remove the drain plug on the water heater. Note - you will get wet. To speed up the draining process, open the lever on the popoff valve at the top. You'll get even more wet....
4) Open the low point drains just aft of the entry door on the passenger side.
5) After all has drained out, close the hatches, and drive slowly in circles on an uneven slope to help drain the water. Park in the original spot.
6) Install an adapter in the city water inlet for your compressor. Blow the lines clear. I did this before bypassing the water heater as I wanted to ensure the low angle of the inlet line after the winterizing valve was blown clear.
7) Close: Drain valve, cap the low point drains, and set the valve on the water heater to the winterizing positions as shown above.
8) Pour in a gallon of pink stuff in the FW tank. I chose to do this rather than using the winterizing line as we are on well water - and I've found leaving unchlorinated water in the tank over the winter can cause issues with mold forming in the tank. The pink stuff stops mold growth.
9) With the unit parked on a slope as mentioned, start the water pump. Hopefully you remembered to cap the low water points - don't ask how I know...
10) Run the kitchen sink cold line until you see pink.
11) Run the kitchen sink hot until you see pink.
12) Run the bath sink cold, then hot until you see pink. This should be very quick.
13) Run the shower cold, then hot until you see pink. Again, this should be very quick.
14) Open the inlet valve to the hot water heater for just a second to push a bit of pink in that low point between the valve and tank.
15) Turn off pump.
That should do it all. The line for the city input should have been empty, so there's no need to add pink to it. You'd need a bit of pressure to get it past the check valve in the inlet anyway.
Hope all this helps!