You could have just tried getting some $20 yardsale/craigslist/thrift store MTB/80's road bike and stripped it. Not saying that would be better but just saying that converting a bike to singlespeed can be very very cheap.

btw your ride is looking pretty cool so far, aesthetically though it might look better with the bars flipped down and the stem lowered (not sure how you fit, but I also prefer a more aero position because I'm into drops and bullhorns).