When you try to jump start it under the hood, the starter immediately spins/clicks even if the key is in off position, is that what you say? Spinning or clicking? Does it turn over the engine?
First solve the jump start issue under the hood. This should be caused by loose cables, bad connection. When you jump start the car from under the hood, the current flows from the source straight to the starter and then it goes back to the battery and then it goes to the front again to supply the electronics. This means that the electronics are supplied by a very long cable which means higher resistance, higher voltage drop specially if you have a bad connection somewhere.
I would start checking the cables on the starter, also the one which goes to the jumper point. The power cable that goes down from the starter into the chassis. The ground cable from the engine to the chassis. If no luck, then check cables around battery,. If no succes, then grounds and power distribution box under the front passanger carpet.