Sharepoint lists question on permission setting vs. custom user views and risks

Hi All,

I'm setting up a sharepoint list to be used by a many people in an organisation > 50. The list will contain sensitive information so it's crucial only specific people see specific items in the list which may contain over 1000 rows of data.

The requirements are that anyone who creates an item (e.g. Peter) should be able to view/edit their item together with their manager (e.g. Simon) plus anyone else they decide to allow access to (e.g. Paul). 

I've looked into item level permissions but found it quite restrictive for how the users would need to use the list. Also given that some of the data might be prepopulated on behalf of users from a starting point so they would not always be the person that created the item. Below item level permissions would not allow manager Simon or additional user Paul to see the item as they didn't create it. Peter would only be able to see his items if he created them but not if an Admin created items on his behalf.

I've managed to get the list to work how I'd like by setting a custom view whereby the user would populate 2 person columns, Column A (Assigned To) and Column B (Manager). By adding Peter and Paul into column A and Simon to Column B I've updated the settings to show only items where their names specifically appear in either the Assigned To or Manager fields. Permissions are then set that users can't un-filter the view.

Now my question is, is this a safe way of allowing users to view and edit their items only based on their name being in either column A or B or is there a risk that other users might be able to see the whole list? Are there any other things to consider with such a list?

many thanks!