The issue with the LT1818 is that its heating up too much, then stops working after 30 seconds, I guess a power down because of the heating. I dont want to use a heat sink.
I also saw the LTC6991 , alternative to the MIC1557 but with 1.1ns rise time.

 

I realized that the LT1818 was getting hot after just a minute.
I just read this in the datasheet:

I am getting 12v differential voltage, therefore I dont think I can use this chip for this purpose.
Anyone can suggest an alternative ? I chose this IC because it gave me 1.5ns rise time.

If simulation goes down to 1V, and real circuit only down to 9V, and if simulation gives a differential input of +/-1V at the inputs, and real circuit 12V, then I would first check the real circuit for errors (soldering, shorts, pin mismatch).
Maybe you won't get the performance and function you need, but it shouldn't be sooo bad...

 

I decided to use the LTC6991 IC to replace my LT1818, there will also be less parts.