I'm not Mike, but....
1. No penalty, it's a corrective distribution with no "adverse" consequences other than not being able to keep the funds sheltered.
2. The associated earnings on the contributions through 12-31 must come out, too. (Or, investment losses would reduce the amount to refund.)
3. It can't stay as a 401(k) contribution - there were no wages to defer from. So if it's going to stay as a contribution to the plan it would be a nondeductible employer contribution, subject to a 10% excise tax to pay and remit via Form 5330. And it will continue to be subject to the tax every year until it can be absorbed under a future year's deduction limit. (If he ends up with a loss in 2022 he'll owe the penalty again.)
--bri