That interpretation seems... odd. You seem to be implying that if your policy is to give everyone a tax credit (i.e. give them money) if you win then you're not allowed to tell anyone about it.

No.

He literally says he'll cut a check for $5,000 for every adult american if the Republicans win both the House and Senate in the midterms.

You don't have to take my word for it: https://www.youtube.com/watch?v=q4NphZBfmnE

He's also stated that he can issue the money without help from Congress, which directly contradicts the idea that it's harmless bloviating about voting in a 120th Congress to implement specific policy:

See: https://www.youtube.com/watch?v=UbLXAdvZcro&t=40s

... though that distinction shouldn't really matter.

The payout is very much a quid pro quo bribe for voters. No additional interpretation of his words is necessary: he's said it very directly himself.