As your links say, both 二百十日 and 二百二十日 are the names of certain folk calendrical terms (210th and 220th days from 立春).
Here, the date counter ～か is used to indicate a day in the calendar. Since there is no serial date bigger than 31 in either Gregorian or Japanese months, thinking about such big dates is usually meaningless. However, those specific two words ...
As you expected, these can be read as とおか but it is not commonly used in daily life.
Same as 1.
=> We say とおか or はつか etc. only 十日 or 二十日, respectively.
六十日=むそか (commonly ろくじゅうにち)，七十日=? (even Japanese don't know. ななじゅうにち or しちじゅうにち are used)，九十日=?
Special case (commonly used now):
初七日=しょなのか (the first seventh day when the soul of a dead person comes to ...