I'm one of the ones here with a sidecar. Unfortunately I'm not sure if I'd be much help with the setup since I bought mine already put together. I can say that the R65 is definitely suitable for one and I happen to have the Velorex 562 on mine so that shouldn't be a problem. I think Marcmax had a 562 as well?
I've heard a lot of folks talk about how the Velorex universal mounting hardware is not all that great. But, iirc, it was usually that it wasn't sturdy enough, not anything with adjustability. Mine has a combo of the Velorex hardware along with some custom bits so, again, I can't tell much about the stock stuff.
It seems odd that it would be so different turning in one direction vs. the other. That sounds like a setup/adjustment type problem but I can't say for sure. One thing with steering and sidecar rigs has to do with the fork rake. The guy who built mine had designed his own triple trees which changed the rake and made steering easier. I *think* there might be a few places that have done similar but, unfortunately, they are never cheap. Same with the Earles forks. With no changes to the forks, steering will be more difficult but I don't recall hearing that one side would be drastically different than the other. As for the bars, I honestly don't know if mine are stock R65 bars or not. I have moved mine around to try and get more leverage and it is surprising how much difference just a little change in angle can make. I intend to try some taller and wider ones at some point to see if that will help even more but haven't gotten around to that yet (since I think that might also require changing cables and the brake line).
If we're lucky, maybe Marcmax will chime in. I think he would be more help than I am since (I believe?) he did more of his own setup and also had a stock front end.
I can say don't give up just yet, your combination should work. It might take a little bit to figure out what the problem is though. I'm happy to try and answer any questions you have.
If you do Facebook, there are several sidecar specific groups there where you might be able to get more input and from a variety of people (that's both good and bad). There is also a lot of sidecar stuff on ADVRider. Let me know if there's anything I can try and answer for you.