@Arjunmm 

I think you are missing one simple but important step: you must manually configure Main Bedroom Deco to connect to Living Room Deco. Place Living Room Deco approximately in the middle between the two, as you did before, then use Connection Preference feature in Deco app to force Main Bedroom Deco to connect to Living Room Deco: How to select a preferred signal source on the Deco App

  @Alexandre. 

This was very helpful. Helped make both 2 dots now. Thank you very much.

Any further tips to make this more stronger like 3 dots?

Thinking of getting another few points as well to a few other places in the house which still need better coverage.

Am I ok to combine X55 with say M4 or P9 decos?

  @Arjunmm 

"Two dots" is usually good enough. If you want more, that would be "three dots" and to get that you'll need to move Deco units closer to each other.

Try that: keep moving Living Room Deco closer to Office Deco unit you see that. You might have Living Room Deco just 2-3 meters (5-10 feet) away from Office Deco to achieve that. 

If you want to add more Deco units to your Deco mesh, you must choose from those that support Connection Preference feature. Otherwise, it'll dissapear from your Deco mesh and Main Bedroom will connect to Office Deco again.

Deco M4R and P9 do not support Connection Preference feature, so I would not recommend those. To be on the safe side, add X55s to your Deco mesh.