You are both currently living off of your inheritance?
Hmm.... I just recently spent 10 months in homeless shelters due to leaving an abusive relationship, so my opinion maybe biased.
At most, I would give him absolutely no more than 2months worth of rent and very basic (utilities like electric, gas, water) expenses. And that is if I were feeling generous and not used.
Yes, the economy is rough right now. But I know of several people across the country (it's not a regional thing) that have searched for and found jobs in the past few months. The jobs may not always pay what they did before or they might be over-qualified for the job, but a paycheck is a paycheck. A tough economy is no reason to not seek employment. If he is willing to not have overnights for a while, he could find a roommate and spend less that way. If he was interested, he could go to school. If he were motivated, he could probably find a job. I suppose it is possible for even the most motivated to not find work.... but I think that those who are most motivated, most serious, are the ones who are finding work right now. Is he really motivated?
Legally, I'm not sure of what the ramifications would be if you provide him any living expenses. We've all heard of alimony, but there is also patrimony, and I don't think you should be stuck with that unless you have a very large sum in the bank and can easily afford to comfortably support him for say the next year. You're inheritance from your parents I'm sure was meant to provide for you and their grandchildren, and of course your dh if he was to continue to be your dh. Since he is not, I'd say he is on his own.
How much? It depends on your relationship. How has he contributed? Are you both SAHM or is he the only SAHM? Was it a joint decision who would SAHM? Or is he unmotivated and simply living the easy life off your inheritance? I hope my questions don't appear ugly to you. I don't intend to be harsh at all. I just want you to look at your situation from all angles before deciding to give him anything. And if you decide to give him anything, I would determine a modest preset limit and once he extinguished that, he's on his own. But I would seek legal advice too and not go simply on this because it does sound like neither of you are working outside of home and that might complicate things.
Best of wishes to you.