he won't be reincarnated into a different race, but the answer to your question is no. overusing any type of Slayer magic permanently changes the user.

I see. I will fix it later then. thank you.

also, in what kind of situation will his Sacread Gear show its true capabilities? A peaceful ine where he is around allies, or under stress when surrounded by enemies?

Azazel is not a 'good guy.' Even in Canon when he was asked about Reynare killing Issei, he was like, "well, you have a powerful Sacred Gear and could end up becoming our enemy." He didn't say she wasn't ordered not to kill him, but straight up admitted he was okay with her decision.

yes

Jewels(the name of the currency. they aren't actual gemstones) can only be earned by doing quests or fighting in the Colosseum. He can't exchange real life money and can't sell stuff in the shops.

Erza over Kiba and Ultear over Gasper for Rias. the rest are the same. Kagura take a Knight piece and Mirajane over Saji, not sure exactly how many pieces she cost.

Maybe. At least she won't be completely hopeless as she was in canon.

Just because he has permission to stay there doesn't mean he has to.

Erza > Kiba

He can reincarnate him.

Thank you, thank you. I don't know if I will add any more 'magic systems.' Fairy Tail already has so many different types of magic, and, well, I'm not very familiar with other animes....

Shameless author here! Can't miss out on giving myself a 5 star review. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

For the magic, I'm thinking about ones from FT. Not sure if I would add types from different franchises. As for the characters, if I decide to add Natsu, for example, I would give him a Dragon-type Sacred Gear with Igneel sealed inside it, so it fits the DxD world.

I'd say F rank.

It's supposed to be a weak to strong type of story. Can't do that if I started him off with some op type of magic. And Azazel is interested in him since he is his first successful product. He'd been trying to create a functioning Sacred Gear for a long time, and finally he managed to recreate his daddy dearest's creation, something no one else had done up until this point. And canon... I'll get to it soon, I suppose. I don't believe I will be following it word for word, but I'm gonna make use of it.

Warrod used Green Magic, which allowed him to control all nature. It's of a higher rank compared to Wood-Make. Though I wouldn't consider Wood-Make as weak since there's that dude called Hashirama who would disagree with me.

Baraqiel is already grieving and Slash Dog is active. It's a bit too late for that. Plus, the MC won't be able to protect the two from the Himejima clan with his current strength. Those guys might not be something special compared to the bigshots of the supernatural world, but they are capable as a group.