This might be a helpful read:
https://www.brentozar.com/archive/2013/09/index-maintenance-sql-server-rebuild-reorganize/

Do not pass GO. Do not collect $200.
Go directly here and read: http://www.sqlservercentral.com/articles/Best+Practices/61537/

You'll get MUCH better answers if you read the article and follow the instructions when...

I guess I'll try to play around with it over Christmas or something... after I rebuild my poor laptop. Thanks!

Is it possible to append anything to the Property column without corrupting the report? Right now, it looks like this:

<Properties> 
<Language>en-US</Language>  <HasUserProfileQueryDependencies>False</HasUserProfileQueryDependencies>  <HasUserProfileReportDependencies>False</HasUserProfileReportDependencies>  <PageHeight>279.4</PageHeight>
  <PageWidth>215.9</PageWidth>
 ...

Sounds like you want use EXISTS, but it's hard to tell without some sample data (CREATE TABLE/INSERT scripts) and an expected output.

So index the Year and Month columns, and then read up on INCLUDE ?

you need to use a filter like this to be able to use your index:

WHERE [DateField] BETWEEN '01-Jan-2017' AND '31-Dec-2017'

Try indexing your date column and then...

There are a bunch of stored procedures that are executed against your tables, right? Maybe use Querystore or something to figure out which queries are being executed most frequently. Look...

Look at the columns you filter and join on. Try indexing those and compare the statistics of your queries before and after...

try
- indexing the fields you're filtering on.
- limiting the columns returned
- add RAM, like to 32GB. 8GB for SQL Server is just painful.

Others may disagree, but I don't know why you would store an instance of a non-event. It's going to make your fact table much larger than it could be. And...

Can't you do something like FILTER() on the DimCourse table to get just the courses you want, then use CROSSJOIN, which creates a Cartesian Product?
https://docs.microsoft.com/en-us/dax/crossjoin-function-dax

You can nest queries if you want... not that big a deal.

SELECT x.Field1, x.Field2
FROM (SELECT a.Field1, a.Field2
             FROM MyTable a
  ...