How to handle unprofessional HR person

Hi there!

I've recently applied to a (development consulting) firm I really want to work at. Their HR processes are a bit of a mess (I applied in September, only heard back in November saying they would send out interview invites that week and then only received a call in January asking me to interview the next day). I interviewed in Jan and my interviews went really well and my interviewers had really great feedback.

I then had a 3rd round interview but I haven't heard anything back (it's been two weeks). I followed up with the recruiter via email and I called him once and he said he would call back but didn't. I followed up and called him again and he said they were still deliberating and that he would get back to me on Monday (3 Feb) but I've heard nothing. If it were any other company I would give up but I've networked at this firm and my interviews went well and I really would like to end up there. Also the fact that they took so long to get back to me between when I applied and the interview leads me to believe that the silence may not mean I didn't get it.

I know a couple of people who work/worked at the firm. I'm thinking of emailing the one person and asking if he has any advice or if he knows if they've concluded with recruiting? Is this a worthwhile idea? Should I try calling the recruiter one more time this week?

Thanks!