You said - "6 lb blackberries, 2 1/2 lb sugar. For a medium bodied sweet I'll use 4 lb blackberries and 3 lb sugar."
Is this per gallon of wine produced? I am assuming not for the entire 30 gallons as this would be a lot less than even a good juice if so.
You could use a Brute garbage can (Plastic) as a primary fermenter for 30 gallons you may need 2). Punch down the cap daily and I would add the campden tablets when you start. This will help to shock any wild yeast or beasties that may be present in the berries. During fermentation you do not need the primary to be completely airtight as CO2 will be produced and will blanket the wine and protect it from O2 exposure. Use the lid for the Brute and some wood clamps to hold it down. Also apply some food grade lubricant to the lip of the container to aid in sealing it up. You can drill a hole in the lid and add a grommet for an airlock if you want to continue using it for the complete fermentation process. When empty, you can clean them out pretty well and use them again . As long as you do not scratch the inside surface, you should have this for some time to use. Another idea would be to cover the top of the Brute with cheesecloth to keep your ants at bay.
Blackberry seeds are quite small and they will no doubt cause you problems if you do not have some means to strain the juice from the pulp of the berries and seeds. Try using paint straining bags to hold you berries in and keep the pulp and seeds contained. Or find another type of bag (nylon stockings might work) if you do not like the paint bags. I wouldn't allow the wine to sit on the pulp to long as it will pick up bitterness from the seeds.
A FoodSaver vacuum system will not be a problem as far as imploding a carboy (IMHO). I also do not think it will have enough vacuum to really tranfer your juice unless the sankey or primary is above the vessel you are transferring to. A 2cfm vacuum pump may however do it for you if your hose diameter is sufficient in size.
I am no expert by any stretch of the imagination, but I have made a few gallons of wine in my time. So take my recommendations as you will and good luck to you.
By the way...... Jack Kellar is a great source of information and using his recipe for any wine is a good thing. The guy has been at this a long time and knows his wine.