Questions: Break Up & Divorce

I am asking this out of curiosity: what does 'cheating' mean to you? I've heard it differs between men and women, and I am wondering if that's true. If generally speaking it is, then it might explain a lot of underlying miscommunications in arguments between couples.

Where do YOU draw the line between "that's fine", "that's insulting (but not technically cheating)", and "that's cheating"?

Note: in the following questions, please consider who "the other person" is to you. That might explain where/why you draw the line. Is "the other person" a random girl/guy you meet who you think is hot? Is this an ex? A best friend? Someone you had a crush on before? Someone who seems interested in you (whether or not you're interested back)? Someone who is openly flirty with you?

If you flirt with someone else, either in front of your partner or behind your partner's back, do you think that's cheating, disrespectful, or just fine?

If you make sexual innuendos (flirt provocatively) with someone else, is that cheating?

If you talk on the phone/text/email/IM, etc. everyday with someone else, is that cheating, disrespectful, or just fine?

If you go on vacation with someone else instead of your partner, do you think that's cheating?

If you hang out with someone else, instead of your partner, and feel closer either emotionally or physically, is that cheating?

If you confide in this other person about fights you and your partner have or other things - things you don't tell your partner for whatever reason - is that cheating?

If you grind on someone else on the dance floor, is that cheating to you? Or disrespectful? Or just fine?

If you go to a strip club, is that cheating? How about if you get a lap dance?

If you touch someone else's boobs, crotch, butt, lips, etc., is that cheating?

If you kiss someone else, do you think that's cheating?

If you have oral sex with someone, do you think that's cheating?

If you sleep with someone else once, is that cheating?

If you sleep with someone else repeatedly, is that cheating?

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For any of the above: how about if your partner does it?

My ex and I broke up 4 months ago and in the mean time he's already met a new girl and has been hanging out with her and stuff. They arnt a official couple or anything and he still doesn't know if he is even going to get in a relationship with her.

Anyways...during that time I've been hanging out with his best friend a lot...who is also one of my best friends too (we were all roommates before). Anyways...we have been flirting a lot and spending time together...ive developed a crush on him now. All my friends say he likes me but I just don't know yet. He has not told me.

While he's been away for work for the past few weeks, he tells me he misses me and that I'm cute and we talk almost everyday. He's back in town now and I don't know what to do...I have not seen him yet...but of course he wants to hang out soon. I feel like this is a bad thing because he is my ex boyfriends best friend...BUT he's also one of my best friends too.

My ex did tell me I can date anyone I want to...and he did move onto another girl about a month after we broke up (we were together for years and engaged too!). That kind of hurt me to see him moving on quickly.

But now I'm over him and I can't stop thinking about the friend...hes so sweet to me.

Should I pursue this or not? Help!