[TomandKarens34]

Respectfully Sir, half a fix is no fix at all. As a wretched junior member I probably have no right to speak with authority on the subject, but I have re-cored a deck. Personally. I will direct you to my members gallery. Alas I took no "during" pictures, but I did about 20% of the deck. I went through the top, cut out the bad core, and reglassed. It took two years. I believe you'll find that balsa is cheaper than foam and works very well as long as you follow Casey's instructions in his book. His method totally seals the balsa so it can never get moisture in it again, so using expensive foam is not necessary. One of the disappointing aspects of doing a re-coring job is there is always more rot than you think. In my case at least 4 times as much. On the bright side my 33 year old '75 O'Day 25 looks almost new. It's resale value is squat but I really don't care. I regret missing two years of sailing. So it remains a personal decision, but it will be a huge amount of work and time. If you're 34 and used to hard work, it won't be a problem. If you're 58, a smoker, have a passion for good whiskey, and work behind a desk, you're in for a trial.
Now for the "suck out the moisture" method. It requires an industrial grade vaccume pump, the one the HVAC guys use. It works on the principal of lowering the vapor pressure of water till it will boil at room temperature. Under ideal conditions it might work, but it is likely there will be an air leak that will prevent you getting a deep enough vaccume for it to be effective. You'd probably have to have it under a deep vaccume for at least a few days for the moisture to migrate through the balsa to effect a complete drying, if you could get that 29' vaccume in the first place. You'd still have bad core which has broken away from the fiberglass layers and is no-longer structurally sound. In my opinion, you've gained little but the knowledge it won't get worse. You still have the problem of a soft, compromised deck. Pouring epoxy through those holes you've drilled it the deck works for bubbles in the deck that are from delamination only where the core is stable and dry and this fix is not suitable for rotten core.
Best of luck.