Should I give up on my marriage?

I have been with my husband for twelve years and most of it has been difficult to say the least. He has substance abuse problems, honesty issues and an insane family. He refuses marriage counseling- we did go once and he was better for a while but he lied and twisted the truth all the way through so no real issues were addressed. But all of that aside, I married him and I am forever endeavoring to make it work. But I feel like I am at the end of my rope and here's why- last night my grade schoolers and I came home and when I got on the family computer which was in the livingroom, there was a video on the screen of two young males engaged in sexual activities. I assume they were not minors but it was honestly hard to tell and I didn't really stick around to find out. There was also a browser opened with two tabs that were both gay porn sites. It appeared there were about five movies downloaded. This is not the first time I have caught my husband looking at gay porn but the last time was many years ago. I don't take issue with the content though as much as I take issue with him leaving it where the kids and I could be exposed to it. Our children, our daughter in particular, are regularly using the laptop for games and school assignments and in fact, as I was opening the laptop to use it, my daughter asked if she could use it next. I know it was not my children. I know it was not there when I was home earlier for lunch and had to use the computer. To my knowledge he was home alone all afternoon and drinking. I was so upset that I confronted him but I was not nice about it at all and so I naturally got attitude back. Our marriage has had issues for some time already but the last time we had spoke at lunch, he was very loving and mentioned that he wanted to have sex with me. I guess because I didn't put out at lunch and instead went back to work, he felt he couldn't wait but the subject matter is disturbing and then leaving it to be discovered is even more so. Should I just give up?