I have a few question/comments
Why is this considered a porous load?
Liquid loads typically don’t have any vacuum because of boilover issues. They will have a purge cycle instead, in which steam enters the chamber at the same time that the chamber is vented (thus the steam and air sweep through and out the chamber together)
The dead end tube length is a pretty big possible source of contamination. Is there another way you can set this up? Can you unclamp the tube, but leave the clamp there (just unfastened) and rely on the vent filter to vent the air. Can you shorten the tube (1.5 meters is mighty long, and would be difficult by itself in a liquid load, even if it was vented on both sides). If you need a long tube, can you put a sanitary connector super close to the bottle, and the other side of the sanitary connector on the rest of the 1.5 meter tube? After sterilization you could connect the tubes to make a 1.5 m tube.
Could you employ sanitary connectors? Could you sterile filter, or e-beam sterilize (thus no need to evacuate the air out). Could you do sterile assembly (in an isolator or hood with proper gowning).
One option would be to sterilize each part, then do a “sterile assembly”. You would have to get a sterile hood or chamber to assemble this together, and follow sterile gowning techniques. You might use a sterile chamber (using VHP or other sterilant) as well.