When normalising, if you have entities with the same primary key, does it mean it should be the same entity?
Place total_extra_item_charges into the same table as the activities. You are unnecessarily duplicating customer_id and activity_d&amp;t for a single column that you indicate will not have more than one row. Try to avoid over-normalizing. 

I would also recommend a primary key on a unique identity column (e.g. activity_schedule_id). Based on your bolding of customer_id and activity_d&amp;t, it appears you're using a composite primary key. A datetime column is not typically suitable as a primary key and is going to add significant physical overhead. I would instead add a nonclustered index and foreign key on customer_id with an include on activity_d&amp;t.

Depending on the transactional volume of this database, you may also want to split the date and time portions of activity_d&amp;t for quicker join lookups. E.g. activity_date and activity_time. Be mindful of the precision level you use for your time - do you need seconds and milliseconds? If you just need to be precise to the minute, be sure you aren't storing this data as you can save a significant amount of space.