Welcome!
You don't have to work so hard. MC has great tagging facilities.
In MC, select all the tracks that for which you want to change the artist (both the correct and incorrect). In the Tag action window, note the artist field. It should say "Varies" for any field where the selections has more than a single value across the selection.
Now, select the Artist field, and enter your correction there. Hit enter when correct. Type-select may help auto-complete the entry for you; if the value is incorrect, don't accept that value, or accept and correct. There is also an Album Artist field. Use this to set a single artist to override Multiple Artists logic in Album Artist (auto) which MC manages and fills for you.
You can also edit in a panes view. Hover mouse over desired column, press F2. If the column for a field does not exist, add it by right clicking the panes view header.
You may have to hit F5 to refresh.