I think the best way to avoid the first ambiguity that could arise by using “finalement” ...
(ie, the one I tried to explain in this comment and which you expressed well in another of your French Language questions as wanting to avoid sounding like [Il s'agit de prendre] la mesure de tout le chemin parcouru (depuis le tout début de [votre] apprentissage des autres langues étrangères jusqu'à ce que [vous vous soyez] enfin mis au français")
... would be to add something like “au lieu de l’allemand” to the existing sentence:
Content de m'être finalement tourné vers le français [au lieu de
l’allemand]!
However, if you don’t want to add au lieu de l’allemand (or "et pas l'allemand") to your nice sentence, I think the best way to avoid all the possible ambiguities that could arise by using “finalement,” including the one mentioned here by Evpok in response to that other question ...
(ie, “[if placed first or last it could mean] that at first you weren't happy you chose French, but that after some time, your opinion changed and that now you are glad you chose it”)
... would be to avoid using “finalement” altogether (which is not totally inconsistent with either the fact that “finalement” was not among your first three choices for "after all" in this question or with Evpok’s correct observation in that response to your other question that even in English, “finally” might imply things that you don’t mean to imply depending on its placement in the sentence).
With all of the above in mind, I think, in English at least, that the notions of “all things considered” or “at the end of the day” would be less likely to be seen as referring back to anything other than your happiness for having chosen French instead of German and that they would also be less likely, regardless of their position in the sentence, to give the impression that you are “finally” happy with the choice, but only after having at first been unhappy with it.
They would of course imply that a careful weighing of the options had occurred prior to you making the decision that you’re now happy with (which is required for all legitimate decisions), but neither of them, in English at least, would imply that you had originally regretted the choice after it was made.
So going from these two notions/phrases as I interpret their meanings in English, I think good French equivalents that you could consider using in your sentence as originally written (without the "au lieu de l'allemand) would include “tout bien considéré” or “tout compte fait” (for “all things considered”) and perhaps a combination of your last two suggestions (i.e., “en fin de compte” + “en bout de ligne”) to get “au bout du compte” (for “at the end of the day”).
As for the position of the above suggestions in your sentence, although the above link to Reverso-Context gives examples of “au bout du compte” being used at the beginning, the end, and in the middle of sentences, I’d suggest, just as Reverso-Context seems to in its examples of “tout bien considéré” and “tout compte fait,” that all of them would be more idiomatic either at the beginning (my preference, except maybe for "au bout du compte") or the end of sentences in general and yours in particular:
“Tout bien considéré/Tout compte fait/Au bout du compte, [je suis]
content de m'être tourné vers le français [au bout du compte] !
