Well issues

[peakbagger]

Interesting. My parents did something similar prior to having a well. 1000 gal water buffalo that would gravity feed to 1500 gal of storage in the house. Jet pump would fill the pressure tank. Worked well but required an entire other building to house the tanks and keep them from freezing. I could envision a bladder under the house if i ever had volume issues but the 7 gal/min is adequate for my needs.

Is there a dc pump capable of 350' pump in a 4" case?

Yup, Grundfoss SQU flex (broken link removed to http://www.sunshineworks.com/solar-submersible-well-pumps.htm)

Of course you need a power source to drive it. Positive displacement pumps don't have usually have issues with depth, centrifugal ( typically AC) pumps are the ones that have a tough time the deeper it gets.