P0401 is insufficient EGR flow.
Nothing about that says to replace the valve.
The passages are clogged.
They clog in the cast piece between the head and the intake manifold.
Your misfire code: Did this happen while driving, steady speed? Post the freeze frame data? Most likely this is caused by the EGR, 3 passages will be clogged up and one will be open. When the EGR is activated, all the flow goes to the open passage and kills that cylinder (misfire code).
Pull the intake, pull the EGR/injector plate, get busy cleaning the carbon out of it.
#7 is the part that needs cleaned, the individual passages and ports get clogged with carbon:
The only thing I have found that fixes this is straight up elbow grease.