1. Congrats.
2. Absolutely power it up. Worst case IF you get another invitation and IF you catch it and IF it has higher IVs is you’ll then have 2 awesome mon. Mine is 82%, and I took it to 40 with no regrets at all.
Edit: I also took my 2nd Mewtwo to 40 as well, and it's a 76%. I have not received an invitation since, nor do I expect one anytime soon given Niantic's recent direction of inviting mostly casual, low-level players over those at higher levels who raid a lot.