DAX: IF 'inside' SWITCH

Hi guys, 

I have this DAX:

Aantal dagen einde contract =
SWITCH (
TRUE ();
ISBLANK(TODAY()); 0; 'Vehicles'[Eind leasecontract] > TODAY(); DATEDIFF ( TODAY(); 'Vehicles'[Eind leasecontract]; DAY );
0
)

What I want is:

If 'tot einde contract' = -1 till -5000: I want this actual number. If the value is < -5000 I want "blank" because column 'Eind leasecontract' is blank, it gives me 01-01-1900. 

So I want something like:

Aantal dagen einde contract = 
SWITCH (
TRUE ();
ISBLANK(TODAY()); 0; 'Vehicles'[Eind leasecontract] > TODAY(); DATEDIFF ( TODAY(); 'Vehicles'[Eind leasecontract]; DAY ); [b]IF 'Vehicles'[Eind leasecontract] < - 5000;  "blank"; 0[/b]
)

These are my columns.

Besides that, as you can see in the screenshot for the upper values, I got date ' maandag 1 januari 1900', which is 01-01-1900. In my database it's a blank, Power BI gives me 01-01-1900 set. I would like to see a blank. If this is possible, I think I don't have to handle the previous problem because it won't calculate Datediff Today from blank.