How can you tell if a guy is actually into you? Do guys act interested even when they're not?

I am completely confused and about to give up on a guy who could be Mr.Perfect, or at least a really fun & cool friend. I'm recently divorced and just started looking around on an online dating website, and met someone . I was not interested at first in this guy. For maybe a few weeks, I'm not sure, he had been checking out my profile, sent a few messages and I didn't respond to any. Then I was about to close my account and figured, he might be a nice guy? Just be spontaneous, you never know. So I returned an email, and we started chatting. He was very sweet from the start, very complimentary. Said I was very pretty or cute. He wasn't like some guys who pretty much want naked pictures or something. We had one date, he was really nervous but we hit it off and he was just so sweet & really funny. I thought, oh, I like him. We were both super stoked, but then the 2nd time we got together was a social gathering, and I brought a friend. Everything went awesome, he was really wanting me to stay the night, but I had my friend. We dropped him at his house where the gathering continued and I got the feeling something was off. I initially said we were leaving, but decided we should stay, by the time we walked back, he was on the phone with who I assumed was one of his kids, his daughter, and he said "be right over sweetie." They live nearby. Since he was off to see his kids, I decided OK, we are leaving, and I'm sure I was acting different, so was he. Then once I got home he kept texting me, saying he liked me. Then said all 3 of us should hang out. And more texts hinting to a 3 way? I was offended. He said he didn't understand. I called him and he said he thought that's what I wanted because of some pics I showed him, and a few other reasons. he stated he was really into me, and blah blah blah. My friend later told me, Oops, she may have made a comment or joke about all 3 of us. So I gave the benefit of the doubt and had agreed to see him the next day & go to lunch. He asked if he could please take me on a real date, etc. But the next day came and he never called, I got a text that night after I had sent a text just saying, I guess you skipped lunch, no worries. I had also left a vm saying I thought he had gotten a bad impression of me. The following day he texted me late at night and asked if we could hang the next day. I agreed, but the next day came and he texted at night saying he had to work all day was tired but wanted to see me the next day. So 3 days now of asking to see me tomorrow, but tomorrow never comes. I'm feeling over it. If he really was busy why not say that? Or apologize? It's weird that he keeps texting at all? Totally confused...
How can you tell if a guy is actually into you? Do guys act interested even when they're not?
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