Pretty sure it's more than that, Idiot Savant grants x5 of the XP along with x 3XP of anything you murder for a short period of time later on, at a mid-level, which then can proc another idiot savant and then it's x3 x5 of the XP, and so on and so forth. It makes 10 INT worthless in comparison.
So I would say it's a far larger amount of grinding than just 30%.
For melee build you need:
1. A melee weapon (melee weapon=/=unarmed weapon). Pikman's blade is pretty good.
2. Power armor.
If you want to winmoar, you need.
1. drugs
2. point or two in little league
If you want to be a god, you need:
1. psycho yao guai roast.
Idiot savant is also more abusable. eg when returning a quest you can save scum yourself a guaranteed idiot proc.
Here's a great melee build to work off of https://www.youtube.com/watch?v=8SCTkpL5dk8
Nerd rage isn't needed. My stealth melee char hardly ever gets below 50% health, let alone the 20% required for that perk to kick in. Got Ninja up, Better Criticals, Blitz, Big Leagues, the usual... but also buffed up Rooted... 2 points in that gives you a LOT of extra damage and damage resistance, as you are usually standing in one spot while meleeing, anyway. By later levels, you'll have plenty of spare points to put into SPECIALs- I went ahead and buffed out END to get Adamantium Skeleton, nice to never get crippled.