If playing a tune in a different key affects the way you decorate it, then so be it. You have to adapt. So what? It means you need to be thoroughly familiar with your instrument.
Exactly. A lot of instrumental music, particularly folk or traditional, is about what feels right to the player. There is a synergy between the player and the instrument. This music is not conceived as an abstract concept on paper such as some forms of art music. In most cases you don't "write" music. The dots are only a rough plan cf. Bach or jazz lead sheets.
It seems to me that an important aspect of this particular discussion is application. What a player should do has a lot to do with the purpose at hand. In this case I don't get the impression that the player's purpose is to progress into being a very skilled instrumentalist, but rather to enjoy music given the time and effort available. In such a case, I'd say do whatever you want to do.
Much of the advice here is quite correct assuming that the player plans to spend considerable time and has aspirations to a much higher level of playing. In such a case it is indeed best to be careful of how one proceeds and the advice give here is what is needed. Of course the recorder is completely chromatic and has immense potential but not everyone aspires to embrace that. Some people just want to play music now. Good on them, I say.
An amateur player is generally used to a relatively narrow range of fingerings, whether formally or intuitively learned. Typically this will be keys like C or F. That does indeed not mean that those keys are considerably easier, just that they are the ones that are first comfortable. One can just as well practice D flat all day and soon become comfortable there. As a serious player, I've done that, but I don't think there would be any payoff for most people. They just want to experience the fun of playing. Again - good on them.