Do I need to update an index include columns every time I add a new column
The missing index code is extremely simple in what recommendations in suggests. One thing is that it doesn't care about selectivity. 

The reason to include columns is to cover a query. I.e., so you don't have to do a bookmark lookup for each row. If you have a rather high selectivity, then these lookups don't matter much, and it is extreme overkill to include bunch and bunch of columns. I.e., skip the included columns and just focus on the WHERE cause and the index keys.

So, don't give those "missing index" recommendations much credit. At all. But they can serve as starting points for your own analysis.

To cluster the "child table" om the FK is another often forgotten trick. As already mentioned by Laughing Vergil.