は and が

I've been reading some books explaining the usage of は and が, but I find myself a little more confused than when I started.

1) I remember reading that __はない (e.g. 行きたくはない、忘れはしない) is used as opposed to the regular negative for emphasis. But the current book I'm reading says it has a nuance of "I don't want to go [but there are things in relation to going I might not mind]" and/ "[other things may happen but] I won't forget." Is this correct? And does it also have an emphatic effect on the verb?

2) If I'm talking with a friend about a movie we saw and she says "あの映画ってつまらなかった", but I enjoyed it, and want to say 私_楽しかったと思う", which should go in the _ - は, が, or do I not even need 私? I thought it would be は for contrast (she didn't like it, but I do) but now I'm not sure.

1)
Yes and no. When は works as a contrastive marker, it doesn't have that nuance, or at least the effect is weakened.

2)
Yes, は is appropriate. When 私/僕 is omitted, a conjunction such like いや、楽しかったと思うよ is needed for the natural flow of the conversation.