Can I Ask Your Advice?

OK bloggy friends...we've been at this awhile now (almost a full year!), so I feel like I can confide in you a bit.  I am a person that is completely an open book, and as such, this blog has taken on a tone of my very public diary at times.  This is one of those times, and I share it not only to get it off my chest, but in hopes that some of you out there will have experiences and advice that can help guide us.
Let's backtrack...about ten months ago, I had a rift with one of Josh's family members (even though I'm an open book, I'm not sure who reads this and don't want to cross any lines, so we're going to keep the details kind of vague).  I viewed the rift as relatively minor, but this family member yelled at me and said some pretty mean things in the heat of it (something I'm completely not used to...my family doesn't fight like that).  A half-hearted apology was given a few days later, and since then we have been trying to move on.
 Unfortunately, though, "moving on" has involved monthly (and sometimes more frequent)angry incidents accusing us (it quickly moved beyond me and on to Josh as well, for which I am actually grateful!) of keeping our son away, treating them poorly, etc.  I, by no means, claim to be a perfect person and look for my fault in any incident, but these have been downright ridiculous: complaining that only one birthday card was given (there should have been 2 I guess...one from Colton and one from us), getting pissd off when calling at 7:30 to say that they would like to visit Colton and being told that was his bed time (has been for the past 11 months or so), getting mad because some clothes that had been given to us (size 18months+ and Colton was less than a year) were not hung up yet, etc..  And just to be clear, these aren't quick complaints...they are knock-down, drag-out yelling arguments (with my husband) that make my stomach turn.
The worst part, though, is that it feels like my baby boy is the pawn in this stupid game.  Over the 10 months, they have shown very little interest in seeing him (maybe 5 times over the 10 months).  Instead, they will call and hint at possibly seeing him, then often back out.  Sadly, it seems as if they are trying to get us to say no, so they can further insinuate that we are not allowing them to see Colton.  I wish I didn't have to believe this, but on the one occasion there was a conflict (I had left the spare car seat at my mom's house after she picked Colton up for us accidentally and not knowing that anyone else would want to get him), it erupted into a major issue where Colton's next visit was cancelled because they were watching a dog.
In short, it has been a very bumpy road...one filled with a lot of negativity, animosity, and not much (if any) progress.  In my usual flee mode, I am at my wit's end and want to completely give up.  We are lucky to have plenty of family members from my side and Josh's (and friends that are like family for that matter) that do love and respect us, and I would much rather surround ourselves with that positive energy.  But...these are Josh's family members, and I don't know if it is fair/reasonable to do that, especially because ultimately I do not want to jeopardize any of Josh's relationships (for his part, he is really frustrated as well, but keeps naively hoping it will just get better...as we progress though and it keeps happening, I wonder when he will realize it just isn't getting better).  Plus, my ultimate responsibility is to protect my son (and our future child), and I want them to grow up surrounded by love, not animosity.
So...this is where I need you.  What do we do?  I'm thinking someone out there has had some similar experience.  How do you make progress with someone that refuses to move on?  And if you can't make progress, how do you maintain some form of a relationship?  Or don't you?