Did James know Snape had obessive and deep love for his wife before he died? and if so how do you think he feeled?

Yeah but did he know even when him and Lily married and had a baby that Snape was still deeply in love with her?

Most likely.

Which is why I have always believed that if Severus had never been in the picture, James would never have noticed Lily in the first place...there were so many other girls that would have had him. Lily was a feather in James' cap. But that's just me.

I think he would have noticed her -- she seemed to be one of very few girls who truly turned him down -- but I don't think he would have pursued her like he did.