+1, safe +4. I say +15 or +16 max would be great.
Leave the enchant rate retail like, or 55% isn't bad too, with those rate, gonna make more challenge for players.
About the epic, make a system, a farming one, like a hard zone, with low chance to drop them ( ike 1/100 ) And each mob have it's own drop.
Or make a craft system, won't be bad too
And if you make raidboss that drop them, make them drop like 3 - 4 or more, will be better if a whole party have to share the drop!
And make some custom area too for the exp and the basic farm.
Make a custom one for normal rb jewel, or make rb jewel only drop able from rb if they are better than the epic one, or vice versa if epic one are better than normal rb jewel
about the enchant, put them in shop, but with a price that will make people go farm for adena as much as possible. Make enchant weap S price for like 30 - 50 kk each in shop.