Do you know what the criminal charge your ex was convicted of? There are many types of related charges that would mean your spouse is inadmissible, i.e. subject to removal and deportation from Canada. (And there are some to which he could have plead guilty that would not mean deportation - and note, it's possible he plead guilty to a lesser charge that would not mean a threat to immigration status).
While this is subject to various appeals and delaying tactics, the authorities do take it much more seriously when the charges involved violence, i.e. will make more effort to ensure someone dangerous is made to leave the country.
Plus: I do not know details but would hope that someone subject to a removal order at some point loses access to welfare and social assistance. (Unfortuantely almost certain that this doesn't happen automatically or seamlessly - different levels of government involved)
All this to say: get in touch with organisations that help victims of domestic violence. There are a number of areas where some legal assistance advocacy might be effective - liaising with prosecutors and knowing which types of charges; ensuring that info is seen and acted on at IRCC level (for potential deportation); etc.
As for the guarantee - it will likley be some time (years) before government acts on the financial guarantee, and there are potential ways to limit the amounts (as above). When the time comes, deal with it then. You may also want to contact MP's office, now and on ongoing basis - perhaps something can be done down the road.
But first priority should be your safety.