Sadly, with meltdowns (I'm assuming this is a display of 'volcanic rage'???) sometimes the only thing to do is walk away - ie, remove yourself from the situation.
Is there a safeguarding issue for him when he has a meltdown? ie, is he at risk either to himself (eg, might inflict self-violence) or to you? That is far more serious alas, and perhaps then you have to report this to his GP, and yours, if they are different.
I would suspect that any attempt to 'reason' with him will be pointless - he's on a bender, and that's that!
How long do they last? What, as BB says, tends to trigger them, what ends them, is there any 'aftermath' and most important of all how frequent are they and what is he like towards you when he isn't having one!
These will indicate whether, sadly, there is 'enough worth staying for'.....the frequency, severity and 'consequences' of them (ie, does he start blaming you, criticising you, verbally lashing out at you, etc etc) could be such that a long term relationship is simply impossible.....for example, could you have children with this man, or is his behaviour such that it would be grossly unfair on a child to grow up with such a dad.....
I would personally argue that the way he is with you when he's NOT in a meltdown is crucial - if he is warm and loving (as demonstrative as someone with Asbergers is capable of, that is - and that in itself can be a source of huge tension in a relationship, alas) then he could well be worth 'investing' in, but at some point you really do have to think 'Is it fair on ME to spend my life with this man, however much I love him, and pity him'.....
It's not easy, alas. Love can go a LONG way to supporting a relationship where any form of 'illhealth' (however defined!) is involved, but it doesn't necessary go 'all the way' .....nor should it. Like I say, your life is important too, just as important as his.
Wishing you well in a difficult situation -
