The new sub-panel is located immediately (about 4") below the main panel and connected to it with metal conduit. To feed the sub-panel, two existing circuits were removed (and replaced by a dual-pole breaker) and those existing circuits were extended to breakers in the sub-panel.
1 - Do the neutral and ground need to be separated in this sub-panel? He bonded them. Most info in the NEC talks about sub-panels in separate buildings or at remote locations. I don't know if the situation changes if the sub-panel is located so closely to the main panel.
2 - The hot wires for the moved circuits were extended into the sub-panel. Do the neutral and ground wires need to be extended also? He left them in the main panel and only extended the hot wire.
3 - Given that 2 20A furnace branch circuits (A/C operation and _electric_ heat) were what was moved, and two additional 20A (patio and landscape lighting & power) branch circuits added, what is a suitable breaker to feed the sub-panel? He put in a 25A and wired the sub-panel with #10 wire, which seems a bit light considering the 2 furnace (heater) circuits.
Thank you for any clarification on these issues.