Is not it a fact that "ignorance of the law is no excuse"? Or is that just on TV?

It's not an ignorance issue. It's not a knowledge issue. It's an intent issue.

You're allowed to give gifts to public officials. What you're not allowed to do is give them a gift in exchange for public services. So in a bribery case, you need to be able to prove that the intent of the gift was to induce the officeholder to do something.

So, if the thing of value is a bag of unmarked nonconsecutive bills being handed to the officeholder in the middle of the night on the third floor of an abandoned parking garage, it's pretty consistent with the parties intending that to be a bribe. But if the thing of value is a Nobel medal being handed over in broad daylight in the middle of the Oval Office in front of the press corps, being covered by the global media, in a big frame that clearly says that it was given from Machado to Trump - with zero effort to conceal the gift - it makes it really hard to argue that the parties intended this as an illegal bribe.

Also, can we not recall him (in principle)?

No. There is no recall mechanism for the Presidency. Again, one of the major differences between our system and the Parliamentary system.