Well... so far, I think you'd get more mileage of your character if you made them with 5e rules. Energy Blast is like Eldritch Blast in damage, however it's stronger than it would be for a Warlock your level given that you add Charisma to damage but at the same time it's weaker since you can only use it once per combat. If you want a pet using Warlock, you could go with Pact of the Chain come level 3 and before that you can have your friend already by getting the Ritual Caster Feat or some other means of getting Find Familiar and then waiting until level 3 for them to be improved. I dunno, it just seems like it may be troublesome for you and the GM in the future as your character progresses and you try to make a character progression meant for 3.5th or 4th edition work on 5th.