All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
As a rule, only the donors (i.e. their intention) can specify if such “allowances and social benefits” are Zakaah or not, since they may intend as Zakaah or Sadaqah in general. However, it is lawful to benefit from them in all lawful and legal activities even to give them again in charity provided that they (first receivers) took these allowances legally as well.
If the government pays a salary to a person who is out of work, whether he is able or not, there is no harm to leave work and be engaged in Da'wah to Allah. But, if the government stipulates one's inability or lack of work opportunity to pay him/her, then here we have to inform those in charge of the true situation, since it is forbidden to cheat them.
Furthermore, a Muslim is advised to abstain from reliance on others, to live on his own licit gain, and to avoid longing for such social benefits and allowances.
Allah knows best.