XPS 12 and Intel HD 4000 custom resolution problems

I have searched far and wide to find a simple solution to this. 

I have an XPS12 with an Intel HD 4000 graphics card.

I know that this card will support 2560x1600 resolution for an external monitor via the mini display port, because it states that in the spec sheet.  I have a new Samsung S32D850T monitor that supports 2560x1440, 60hz resolution.  However, I cannot change the resolution to this by means of display settings AND I cannot create a custom resolution for this monitor because I keep getting the "custom resolution exceeds the maximum bandwidth capacity" error.

I have read about how if you "clone your display" it will only support the highest of the two displays (which in my case is 1920x1080 from the built-in display).

I have an active mini display port to HDMI that I have used on my old monitor (Samsung 24") just fine.  I've never thought about changing the display resolution before.  But since the Windows 10 upgrade, the graphics have become worse.  And the newer, bigger, monitor only amplifies this terrible display where everything looks blurry.

Please understand that the built-in display is working just fine and everything looks great on it.  But for work, I cannot use that little display to carry-on daily tasks.

I have set the scaling to 100% instead of 125% and it helps some, but the text and is so blurry on this post, that I have to make sure that I haven't double-entered "l's" or "i's" because they all look the same.

Please Help!!!