1.I think the lower ranked members is never going to rank up to legendary.
No you can be a legendary if you posting high quality posts and post that may be helpful. only shit posters will never attain the legendary rank.
2.Soon there maybe a merit farming.
I don't think there will be merit farming since just like trust everyone will see the user sent/received merits it will be easy for DTs spot the account farmers
3.I am sure that not all the quality posts will get merits.
I agree not all quality posts will merited but you have a high chance that you will be merited.
4.Mods,DT,merits sources are exchanging smerits between them.
No. I think mods and DTs will be fair and square when it comes to meriting someone.