Do you think that it is possible/realistic for a 40 years old woman with very rusty English grammar to move to Poland and stand in front of a lot of enquiring minds, whilst hoping to remember my own name and get through the day ?
Yes. For one simple reason - there are very, very few women in Poland teaching English, and even less who have some decent experience in life. The industry is dominated by male native speakers - which will make you stand out, especially in a place like Torun.
It's worth pointing out that while knowing the grammar is good, many people aren't interested in being taught grammar from a native, but rather connecting with the language itself. You're in a really great situation - you won't be perceived as a "kid" by ageist Poles who feel that age = respect, and you're also very sellable as a female native.
Also - unlike male native teachers, you'll have the great ability to persuade parents to sign up for lessons with you, especially with younger children. You can make a hell of a lot of money from parents of youngish children :)
I entered a 'Talent Show' in Torun last year. It took me three months to properly learn, by heart, the song I sang. That is a month a minute ! Do you see why I am worried. Lol.
The fact that you had the guts to do this tells me that you'll be a great success in Poland. :)
The key skill with teaching English isn't an exhaustive knowledge of the terminology and metalanguage, it's an ability to help your students learn - to make sure they leave the classroom with something new that they can use.
And in all honesty, that's what works for me. I'm not a great grammar teacher (I don't like it, don't have any passion for it) - but I seem to be able to help people learn new things. Everyone is different - you really don't have to be a great grammar teacher in the beginning in order to be a success.