Hey there! I'm brand new in here, but so excited to finally be at home!
I'm no expert, just used to messing with wires. I second the recommendation, although I'd try to remove the stub from the positive post altogether, run a new one from that side to the stub you snipped on the side going to the voltage regulator of the starter. This will effectively remove "junk wire" where possible and complete the recommended solution as previously stated. The ammeter is just a measuring tool effectively completing your circuit. Do, when you remove it, you need to close the circuit back somehow, as explained now. Hopefully that explains the logic and next time you remove a "measuring instrument" you'll be good to go all on your own! But certainly we're always here for questions too. Happy wiring friend!
I know I'll need tons more help than this as I dive into my first rebuild, and I'll be humbly reminded of how much more I don't know than what I do know! Ha! Let us know how it goes!
-Grace and peace,
James.