I tweaked all pacts upwards.
Pact of the Blade can make ranged spell attacks as melee spell attacks using their pact weapon. They get a bonus to damage equal to 1/2 of their strength (rounded up), or dex (if finesse weapon).
For EB, I changed it to a standard cantrip (1d10 per tier damage). I then added a Warlock feature at 5/11/17 that lets them "split" their cantrip dice. For attack cantrips, they can target the same creature repeatedly; for non-attack cantrips, the targets must be separate.
I also made the agonizing blast apply to all warlock Cantrips, and be free at level 2.
This means you can play a Warlock that does a firebolt instead of a EB, or even one that uses debuff cantrips.
For Chain, I gave the familiar +3 HP/warlock level and +warlock prof mod to attacks, saves, AC and damage. In addition, when you tell the familiar to attack, it will continue to attack the same target if you don't stop it.
For Tome, the tome works as an arcane focus. While you have it in your hand, you can expend an action to regain a warlock spell slot. You can do this again after you complete a long rest.
For Hexblade, I changed "replace your attack stat with Cha" to "You add Cha/2, rounded up, to your attacks and damage with the weapon. If you bond a magical weapon, you instead add +1 to attack and +cha/2 (rounded up) to damage." This removes a few charop tricks (GWM+Elven Accuracy) incidentally but is mainly aimed at "it isn't only your mind swinging the sword" (verisimilitude).
(I also did some stuff to Hexblade's curse).
These are aimed at making the 3 pacts more distinct built-in.