Superb insights Ross - thanks for the share! I project managed (& co-wrote about 5% of the code) & sold some SMS software a few years back, and probably made all the mistakes you detail above. It did do some sales, which I was able to live off for 6 months, but I really didn't know what I didn't know when it came to managing the whole process & consequently probably missed out on 10X in sales.
However - it was a superb experience, and well worth doing, and looking back now, it gave me massive confidence to create new projects and push things forward.