"I can avoid penalty on missed 401k distribution, if the amount distributed from IRAs (line 53)
exceeds the amount of RMD which is IRA RMD plus 401k RMD. (line 52)"
False. A distribution from an IRA can never be used to satisfy an RMD for a 401(k). The RMD for the 401(k) can only be satisfied with a distribution from the 401(k). To correct a missed RMD for the 401(k) you must take the late distribution from the 401(k). This will mean taking from the 401(k) in a single year both the late RMD for the past year and the RMD for the current year, and both will appear as income on the tax return for the current year.
Note that because an RMD for a 401(k) can only be satisfied from that RMD, the plan knows when an RMD is required for a particular year and the plan risks disqualification if it does not force out an RMD by the deadline for making the RMD, so it's odd that he 401(k) plan did not make the distribution automatically to avoid a missed RMD.
