blended families and discipline

Hi ladies, I'm looking for advice on blended families and how others make it work! My husband and I usually have our kids at seperate times (when his are with us mine are with their dad and vice versa) but for the school holidays and stuff we have them all together. He has always let his kids (who are 13 & 15) pretty much do whatever they want but he gets cranky with my kids (10, 7 & 5) for every little thing. We have talked and agree all kids need the same rules. Now me and him are constantly fighting because he thinks my kids are naughty, I'm constantly telling my kids off and his kids are still getting away with everything (just today, they've called him gay, an idiot and told him to f*** himself as well as bullied my kids, been rude to me and broken things that aren't there's with no remorse and no attempt to do anything about it and he has done nothing) they don't listen to me at all and when I try to talk to my husband about it he just points out what my kids have done wrong (so far, today all that's been is not put away toys when they were finished with them, and I dealt with that straight away). I feel like if things stay like this we will break up cos I just can't handle the constant fighting and my kids havestarted saying if they can do that why can't we? Which I think is quite reasonable and my only response is the rules in my house have never changed, never will and my step kids aren't mine to discipline but even to me that doesn't sound fair. Help!