I have got the first 4 points.

I tried the third trial of sekhemas and failed and no longer have those baryas level 60+.

Is it possible to buy them from the site, i.e any barya over level 60 is a 3 boss one?

Or do i need to farm it manually and are character specific.

You can farm them manually or buy them from jsp.
You can also request the service for someone to do it for you.