Engine stutters at half a tank

That description sounds like a fuel pump issue inside the tank. The pump is getting weak and without the full tank of fuel to force the pump to work better you get the lower power. A simple fuel pressure test would verify it. Try this and see what your pump is doing. You should see 35 - 70 PSI on a good pump and control module.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator