True enough. However, one nitpick. Nothing wrong with using identities as a clustered and primary key. Mind you, my experience is designing "small to medium" OLTP systems (read, around...

??  Nothing's changed in that query.

...
from
(
select B.company_name as Company
,SUM(CASE WHEN IssMth = 1 then (CashOnly) else 0 end) as Jan1...

SELECT ID, FIRSTNAME, LASTNAME,
  FIRSTNAME + '.' + LASTNAME +
   CASE WHEN row_num = 1 THEN '' ELSE CAST(row_num - 1 AS...

Those requirements seem contradictory to me.

What I need help figuring out is how can I see if 
All of the Difference columns are > 1 (meaning there...

Copy the :
where SplitEmpID is not null
check into both the inner queries so that it execs before the UNION A-L-L, not after.

If you at all can, change...

Also, you need to either:
1) check the number of logical log files
2) shrink the log as much as possible, then immediately reallocate it in large chunks.
2) is easier...

I have a little more time today, corrected version below. 
The cte is to (1) make it easier to use in a function and (2) to make it easier...

As usual with age, leap year birthdays are the deciding factor.

If someone was born on Feb 29, 2004, how old are they on Feb 28, 2018?  In your...

No.  In fact, generally they are a bit faster since you don't have to decide within the trigger which action -- DELETE / INSERT / UPDATE -- has occurred.