You posted the request here and it sounded as if you wanted feedback. That’s why I responded to you. An assessment largely depends on the percentage at which you are financing the construction project. Without that information, it is difficult to make a statement.
Regarding the reliability of construction financing calculators, I can only speak from my experience. For my first construction, I ultimately received a better offer from a local bank than through the construction financing calculator. For the second construction, I found a broker via the construction financing calculator who brokered exactly the offer that was presented in the calculator. Interestingly, this was also a local bank whose terms were so much better through the broker that the caseworker did not believe it was an offer from his own bank when signing.
Banks know that they are only relevant for online distribution if they appear on the first results page. Ideally among the top 3. That’s why you often get completely different terms there than when you ask the bank directly.
Regarding the special repayment: You may be offered 10% without an extra charge for a loan of this size. This was the case for me, for example, with the second construction. If you have the 85k included in the main contract, then you can incorporate a possible excess proceeds from the apartment sale into the financing through the higher special repayment option without time pressure.
That you will get 85k more from selling the apartment is only certain once you have a solvent buyer who pays the 85k more. Until then, it is an expectation you have. I would not rely on that.