You can run it off of 12v, but then you would need to divide it back down to 0-5v. The FB only supports 0v-5v input, so sending in 12v would release some magic smoke.
The resolution is determined by the PIC. We have 10bit resolution. Some people have 8bit, others 12 I believe (in a similar to 3 times price range, but they obviously go much higher, think premium sound cards ). So 10bit resolution is 1024 available steps. So 150PSI divided by 1024 (2^10) steps, means you have a 0.14PSI resolution no matter what. If it were 8bit, you would only have 0.6PSI/step resolution.
How accurate are you looking for?
And I have my final exams this week, and then I leave out of the country on the 20th, so I will try to get Uber "releasable" after exams, and before me leaving, as internet on the island is spotty at best. I think it is just a few satallite dish's splitting the internet over the whole island, so no uploading of big files, that is for sure.