27" Dell - Display and scaling issues on Windows 10 (3 monitors - 4k display + lower res)

Hi,
Recently I purchased a new Dell 27" 4K monitor and upgraded my machine from win 8.1 to win 10 in order to get better support for higher DPI for my multi monitor rig.

Here are when the problems started:
1. the main problem is that with the main monitor (Dell 27") set to 175% scale (looks good) the two other monitors are set to 100% scaling - (icons/text looks giant - basically almost unusable). If I set it to a lower scaling (on the 4K monitor) I can't read the text or see the icons as they are so small. 
2. When the monitors goes to sleep things get massed up - icons on the main monitor turn tiny and open tabs on the main monitor move to the one of the other monitors for no reason.

My system: 
Intel 5820k - 6 core + Asus X99, 32GB ram. Asus GTX970. latest nvidia drivers.

Displays: 
1. 27" Dell P2715Q 4K - main (connected using DP).
2. 24" Dell 2407DFPHC 1920x1200 (connected using DVI).
3. 23" LG 1680x1050 (connected using HDMI).

I talked to MS and the representative (who had really poor English and I am not sure knew what he was talking about) said that the only way this will work is if I connect the 2 lower res displays to a second GPU. I have a few but they are old GT210 is the newest (I have 8800GT which is super old). I tried to connect the GT210 but it is not recognized by win 10 and I can't seem to install it along with the 970GTX to see if it will work or not (buying something newer just for the very low chance that it will help seems kind of silly).

Ideas on what I can do?
Iddo