You do not need an R-2R ladder to make a simple D/A converter. The original circuit will work, but you have the bits reversed. You need the smallest valued resistor (R)on the MSB, 2R on the next bit, 4R on the next, etc. See the revised schematic below. The color coding follows your original notes. You can make a perfectly useable DAC in this manner, so long as you don't want to go too fast or have too much resolution.
Having said that, you will have tuning resolution problems if you want to make a receiver. You might get by in a simple transmitter, but your channel spacing will be non-uniform because of the voltage-vs-capacitance curve of the varicap.
Also, at zero volts bias, the sine wave on the diode will forward-bias it on a portion of each cycle, which will probably cause you all kinds of grief.
You would probably be better off to use 4000 series CMOS so you can build in a reverse bias at zero code to prevent this problem, and also get a wider tuning voltage range.