I bought a new set of chain tensioners because the old ones made a lot of noise.

The ones I replaced, that came with the bike, were plastic. I got new ones with ball bearings hoping it would get rid of the annoying sound. It did 50% but I still have this sound:

https://youtu.be/t-IRsMOcoWs


Is it normal? Can I do something about it?

I also have this "sand in the chain" sound at the back sprocket. I cleaned and lubed the chain and also cleaned both sprockets and anything around but I still have that sound. I assume it does this because the chain moves left-right which brings me to my third issue.

The chain has started to rub on the new tensioner but it's not centered, it's a lot to the right (there's just a bit of extra rubber left on the interior side). Should I try and center it or just leave it like this? And if it need centering how do I do it?

Is an extra chain tensioner like this one worth buying? Does it help in any way?

And while I'm at it, can someone recomend me a lift stand? The stander I have now is pretty lame and it works on the back wheel only.