Experience

 per Level has been changed to Vanilla Fallout 4. You need thousands of Points to reach another Level.  gained by crafting is close to 0 and only some items will yield XP. The Survival Stats Menu (Field Kit) display your exact numerical XP and XP needed to next level

Gaining

 * attach certain Item Mods
 * Weapons Lab: Weapon Tinker Kit (ZX-1 Experimentation Lab) +150 XP per use
 * Reverse Engineering (ZX-1 Experimentation Lab) +25 XP / Weapon
 * Educational Material: Some items that grant XP upon consumption, will also give you Educational Material when you consume them
 * Crafting and Building no longer gives tiny bits of xp
 * Gaining the "Gift of Gab" Perk
 * "Well Rested" Status will yield +10% XP for a limited time

Lockboxes / Electronic Lockboxes



 * Basic Boxes don't require any skill, and give +5 xp
 * Standard Boxes require 90 Lockpicking Skill, and give +15 xp
 * Complex Boxes require 180 Lockpicking Skill, and give +30 xp
 * 80 Skill ~ 25 XP
 * 140 Skill ~ ?
 * 180 Skill ~ ?
 * 200 Skill ~ ?

Research Notes

 * Using these items will instantly grant XP
 * This item is located in the "AID" tab
 * can be found on some NPCs above certain level ranges
 * can occasionally be found in Loot
 * Settler Missions have a chance to bring them back

Idiot Savant

 * Idiot Savant is reduced to 2 ranks, and its xp bonus is rescaled to be smaller but more often
 * Rank 1: You randomly receive +50% XP from any action. The lower your Intelligence, the greater the chance
 * Rank 2: You randomly receive +50% XP from any action, but the chance is doubled

Awareness

 * Rank 2: Learn from your enemy's mistakes. For every point of Perception, you gain +3% XP per kill in combat (up to +30% XP maximum.)

Enemies

 * XP for sub-types is normalized better, but varies based on their specific difficulty
 * All legendaries give double XP

Slayer Perk



 * You gain bonus xp for the first kills of each enemy type (varied based on type)
 * Bonus xp drops to 0 once you reached a preset limit
 * Bonus xp is not modified by xp penalities or buffs (intelligence, debuffs, etc.)

Lowering

 * any Tier in "Thirst" (Parched > Severely Dehydrated) lowering your INT will yield to less XP
 * some Chems will lower INT when getting an Addiction

Leveling
The Vanilla Leveling System has been altered.

The experience points required for level n can be calculated from the following expression:

$$\Delta\mathrm{XP}_n=300\cdot n+500\,$$