Sorry, you don't qualify for common-law as you've not lived together for the required 1 year. I think your best chance here is to get married and try a spousal application. Technically, you're just dating (or are maybe engaged) and that's not valid grounds to give him permanent residency.
He's allowed to visit you in Canada while the application is in process, but be advised that sometimes a tourist visa can be hard to get at that time. Sometimes immigration feels that the person applying doesn't intend to leave Canada when the visa will expire and so deny it. And even if they grant it, he could have trouble getting into Canada when the officer finds out he has a permanent residency application in process. He might be asked to prove that he intends to leave (return plane ticket, proof of owning property back home etc) upon entering.
Having a child together usually helps prove the relationship is genuine and could possibly help you in the sense that they're more likely to skip the interview. You still have to provide plenty of relationship proof though, so be sure to keep records of your communication, any trips together, take plenty of pictures and just basically document as much as you can. Other than that, it won't really speed things up, there's no priority processing for cases like yours if that's what you were hoping for. But, since he's from Croatia/Bosnia, you'll probably want to go through Vienna and they have a pretty decent processing time, especially compared to some other visa offices. If he's lived in several different countries though, the background checks could take a while.
Hope the information helps at least a bit. Sorry, it's probably not what you were hoping to hear. I wish you two good luck with getting together
