Renting is not dead money. You get the use of the apartment for the rent.
You could equally argue that paying mortgage interest is dead money. You get the use of the money for the interest.
You illustrate this perfectly well yourselves. If you had bought the house 2 years ago as planned, you might have saved yourself €24k "dead money", but your apartment would be worth €200k less now. So you have got a great return on your "dead money".
You can start saving immediately, by using the shares in the Credit Union to pay off your loans. You are probably paying a very high interest rate on the loans and getting little, or possibly, even nothing, on your shares.