Your pitch temp shouldn't cause a problem. If anything, it would cause it to be cleaner tasting.
As far as the mashing, it's an interesting question, and I'm not exactly sure what you'll get, but in theory, at 137 you shouldn't have been converting to sugar but just breaking down proteins. At 150 you would be converting to sugar, but not very long. But I think it will probably be ok because some people say they get a complete conversion in 20-30 minutes. All the time the temperature was rising from 140-150 it would be converting, plus the 15 minutes, plus the time it took to rise from 150-158. All together it would be sufficient time probably. Maybe not as good as holding it for the 60 minutes, but good enough.