High likelihood I'll be unable to submit my thesis before the deadline... What's my outlook?
The situation you are describing might sound like a difficult one, but I am pretty sure that if you go and talk to your doctoral school you will find that is not an uncommon one.
Instead of relying on what your supervisor says, you should probably just describe your situation to your doctoral school and see what possibilities are before you. It is, in a way, the role of the doctoral school to provide counseling in such cases.
In the meantime, if you do not know what ATER are (Attaché Temporaire d'Enseignement et de Recherche), have a look at these specific positions. They are sort of TAs positions. The link is in French, but in your case, the most important sentence might be:

Pour devenir A.T.E.R., il faut être dans l’une des situations suivantes :

[...] soit être inscrit en vue de la préparation d'un doctorat, le directeur de thèse devant attester que la thèse peut être soutenue dans un délai d'un an ; [...]


This means that you are eligible for such a position, only if your advisor is positive that you can defend within a year.
Finally, while your experience feels wrong, you sound like you have learnt quite a lot from it. I guess you should focus on finding the positive sides your experience.