Never use ISNULL in a WHERE clause: not only is it unsargable [not relevant in this particular case], but it can also make the code harder to understand.  The code...

The single most important thing is to do a logical data model before doing a physical database model.

Hints:
1) Google "logical data modeling".  
2) Fillfactor, indexes...

select 
SUM(CASE WHEN TYPE ='D' THEN 1 ELSE 0 END) AS 'TotalXRows',
SUM(CASE WHEN TYPE ='L' THEN 1 ELSE 0 END) AS 'TotalYRows',
SUM(1)  AS 'TotalRows'
from dbo.Table with (nolock)

I'm not entirely sure of your intended search rules either, but as best I can tell I think this should get you close:

WHERE ColumnName + '.' LIKE '%[^0-9]1...

There's a huge difference between with and without a default.

If there's a default value, SQL has to modify metadata and add write that default value to every row...

I still believe what should have been done, and what could still be done, is that the value should be in its own column.

You can always add columns...

WHERE dbo.LogFile.Created >= DATEADD(month, DATEDIFF(month, 0, @mydate) - 12, 0) AND
  dbo.LogFile.Created < DATEADD(day, DATEDIFF(day, 0, DATEADD(month, -12, cast(@mydate AS date))), 0)

Edit: Corrected calc of ending date.