Not sure anybody can give you a sensible answer due to the vague nature of the programme.
Unlike the I 134 and the I 864 there are no set numbers, they do imply that they use the Federal Poverty guidelines despite that level of income being unable to realistically support a family of 5.
And then the requirement is to be willing to support, now the I 134 is not enforceable and the logic should follow through to the I 134a and it does say willing not must. I am not aware of any court cases so who can be certain?
I would have thought $300k cash would be good, if that is the house you live in not so good.