It's the 1/4" copper that is the problem. You have 30/50 pressure at the tank. A new tank willnot help. Depending on the pump, you may be able to turn it up to 40/60, which would help a little. The hose at the tank works good because it is bigger. Run a hose to the sinks and toilets and they will have good pressure as well. Not a long term solution though, gonna need bigger pipe.