Optimizing Measures to avoid Out of memory errors

I need help in understanding how to optimize some measures and have a few questions. My system configuration is :

• OS : Windows 10 (64 bit)
• Memory : 8 GB RAM
• MSOffice : Office 2016 Pro (64 bit)
• Page File Size (Minimum MB) : 12888 MB
• Page File Size (Maximum MB) : 49152 MB
• "Disable Hardware Graphics Accelaration" is checked.
• "Ignore other applications that use Dynamic Data Exchange (DDE)".

I am using PowerQuery to import 1.12 GB of external CSV data from multiple CSV files. After transforming that data by removing unnecessary columns, changing formats etc and adding to PowerPivot Data Model, the size is now reduced to 555MB.

I have created 2 tables in PowerPivot:

1. fData table from multiple csv's.
2. dDate table from a linked spreadsheet table. I have then deleted the Spreadsheet table and removed the link from dDate table.
3. dDate is linked to fData on Date ---> Item Appearance Date.

I have created a Simple Pivot and added Slicers on sheet for the following:

1. Year (from dDate table)
2. Country, Category, Brand Owner, Char Description, Char Value (from fData table)

I have the following measures created:

DistinctCount:=DISTINCTCOUNT(fData[Char Value])

TotalCountWithAllFiltersRemoved:=IF(CALCULATE( COUNTA('fData'[Char Value]), ALL(
'fData'[Category],
'fData'[Country],
'fData'[Brand Owner],
'fData'[Item Appearance Date],
'fData'[Char Description]
 )
) = COUNTA('fData'[CHAR VALUE]), COUNTA('fData'[Char Value])
)

UniquesCount:=IF(
	HASONEFILTER('fData'[Category]) 
	&& HASONEFILTER('fData'[Country]) 
	&& 	HASONEFILTER('fData'[Brand Owner]) 
	&& HASONEFILTER('fData'[Item Appearance Date])
	&& HASONEFILTER('fData'[Char Description]) 
	&& HASONEFILTER('fData'[Char Value])
,
[TotalCountWithAllFiltersRemoved],
    SUMX (
        SUMMARIZE (
		'fData', 
		[Category],
		[Country],
		[Brand Owner],
		[Item Appearance Date],
		[Char Description],
		[Char Value] 
        ),
        [TotalCountWithAllFiltersRemoved]
    )
)

UniqueChars:=IF(CALCULATE( COUNTA('fData'[Char Value]), ALL(
'fData'[Category],
'fData'[Country],
'fData'[Brand Owner],
'fData'[Item Appearance Date],
'fData'[Char Description]
 )
) = COUNTA('fData'[Char Value]), 1
)

UniqueCharsCount:=IF(
		HASONEFILTER('fData'[Category]) 
	&& HASONEFILTER('fData'[Country]) 
	&& 	HASONEFILTER('fData'[Brand Owner]) 
	&& HASONEFILTER('fData'[Item Appearance Date]) 
	&& HASONEFILTER('fData'[Char Description]) 
	&& HASONEFILTER('fData'[Char Value]) 
,
[UniqueChars],
    SUMX (
        SUMMARIZE (
		'fData', 
		[Category],
		[Country],
		[Brand Owner],
		[Item Appearance Date],
		[Char Description],
		[Char Value]
        ),
        [UniqueChars]
    )
)

My Questions:

• Measures Issues:
  • Is it correct to base the Year Slicer on the Year field in the dDate table, instead of Item Appearance Date from fData table?
  • The above measures "UniquesCount" and "UniqueCharsCount" when applied to Pivot, do not give the Unique Char Values that appeared every Year. This is evident when i apply a Conditional formatting on the Char Values list for Uniques. Such Char Values newly appeared in that Year i.e. they do not repeat every year. How do i create such a Meaure?
  • I would also like to find the Unique Counts of Char Values for SAMEPERIODLASTYEAR. Such Char Values newly appeared in that Year i.e. they do not repeat every year. How do i create such a Meaure?
  • How do i also show the FirstDate a Char Value appeared in a particular Country (i.e. Market) or Category or for a Brand Owner (i.e. Manufacturer)? How do i create such a measure?

• Memory issues:
  • If i add the DistinctCount measure or add a "Distinct Count of Char Value" or a "Count of Char Value" in Values section of Pivot, the Pivot table calculates and renders quickly. But if i add any of the other Measures, it mostly results in the following Memory error:
  • 
  • How do i optimize the above measures for better and quick performance?
  • Why should the file size show 555MB when i have loaded external data as Connection to Model? Is it because i had clicked saved data to model? How can i conveniently share this file easily with others excluding the large size?

Any help would be most appreciated.