I've recently purchased this silicone and a pump. I've watched your videos and admit that I'm new to all this.
But does this stuff go off? It seems VERY thick.
I mixed to 10% by weight, stirred slowly to avoid bubbles and trickled from the mixing cup to a wide-bottomed container within my vacuum chamber. This seemed to create more bubbles that I already had.
I turned on the pump and sure enough everything expanded very quickly... but it NEVER collapsed. Several minutes went by and I gave up.
I trickled over the pattern and could see loads of bubbles. It took over 5 minutes to trickle less than 100g of silicone. Is it always this slow and resistant to movement?
I placed the pattern in the vacuum chamber.
Quick expansion of bubble... never collapsed.
Does this stuff go off? Am I missing a step? I have far too many bubbles setting within the silicone.
Here's a video of the whole affair if it helps : https://youtu.be/JcAs4bQkRGc
I sped the whole thing up by 20x as it's so slow.

My first suspicion is that your vac chamber doesn't actually get to full vacuum. I know you say it's air tight, but how do you know? Does it have a vacuum gauge? Can you pull a vacuum, switch the pump off, and come back a few hours later to find it hasn't leaked at all? 

To me, it looks like the silicone want to collapse but it's only at about 90% vacuum. Everything happens in that last 10%, so if it isn't actually getting there then it won't collapse.

Otherwise, what temperature is it where you are at the moment? If it is cold, the material will be significantly thicker. I can't really see a whole lot wrong with your silicone, although I dont know EC's silicone at all. If it cures though, it isn't expired. Viscosity really shouldn't prevent a material from degassing, it may just take longer.