On the layout I should be able to type in Opportunity ID (only once)
That can be a problem right there. It's better to have OpportunityID be an auto-entered serial number that you do not have to enter at all but rather is entered for you when you create a new record in the Opportunity table. If you have another ID from external sources, define that as a field in Opportunity, but do not use it in relationships as this can cause problems for your data if you do.
his data should then automatically fill the Opportunity Table and the Events Table.
Actually, this data sounds like data that should only be entered in one of the two tables. Your relationships then make it possible to combine the data from the two tables in one layout or report. Entering the same data twice creates a number of potential problems and is not needed. For example, you'd enter Opportunity Date once in the Opportunity Table, On a layout based on events, your one to one relationship makes it possible to add the opportunity Date field from opportunity to the Events layout and the date will be properly displayed and even editable should you want to make that possible.
In fact, with your one to one relationship, you can put all the fields from Opportunity, Funding, Tutoring, LearningOp, Events, Experiences all on a single layout based on Opportunity. If "allow creation of records via this relationship" is enabled, you can simply enter data in all of these fields as though it were a single record in a single table as long as you have a value entered in OpportunityID--which should be the auto-entered serial number so that this happens automatically. If you wish, you can place the fields from the other tables each in different panels of a tab control to better organize the fields for each table by type.
That worked! Thank you very much :)