nice work on the build this is going to look sweet when it's done. You used my favorite color too! As far as removing a freewheel goes^ As long as we're not talking about a casset here is what to do.
1. buy the specific socket for your type of freewheel (less than 10 bucks)
2. put it on the free wheel and hold it on by putting the axle nut back on
3. clamp the socket in a vise or get a really big wrench
4. If it's in a vise then now grab the wheel and turn it counter clockwise
5. Now that the freewheel is off place it on a board and use screws between teeth of the largest cog to screw it down (don't worry about bending it because you won't use the largest one)
6. Use a chain-whip (or fab one up with an old chain it's easy!) and unscrew the smallest cog. This step is easiest if you clamp the board to a table in the vise or get some friends to stand on it.
7. lastly choose the cog size you want and using either pvc bits or the spacers that were on the freewheel get it in the center and use the smallest cog to hold it all on there.
BAM you now have a single speed bike with no whee dishing or buying a single speed cog. Also if you do it correctly you can change the gearing if you don't like it.
this is a single speed I built this way except no spacers or lock ring/cog because it's an old 2 step suntour freewheel with more threaded cogs.