We have a KSOP where the plan sponsor wants to terminate the ESOP portion of the plan but retain the 401(k), matching and profit sharing portion of the plan. We want to submit the ESOP portion of the termination to the IRS for a favorable determination letter upon termination. Can we do this? How is it done? What other options are available? One thought is that we could spin the 401(k) portion to a new plan and then close current KSOP plan. Does this sound feasible?

[1] Yes.
[2] Several possibilities. Easiest would be to amend and restate into 401(k) plan with frozen company stock account.
[3] Split plan into 2 plans; create new plan and roll over; terminate old plan, etc.
[4] Yes, it sounds feasible.
You omitted stating whether the company is to redeem the stock now, or leave in plan until employees are in pay status. Be careful, since some approaches will result in full vesting and others may not.