You're going to have deliverability issues with Gmail no matter what if you roll your own. I had ran my own mail server with SPF/DKIM/DMARC/etc. for 15+ years, all setup correctly and still had no guarantee that messages would inbox. I finally gave in and switched to an offshore 3rd party service for hosted emails to keep the "I wonder if that important email actually got delivered to their hosted Gapps" at bay.

But you cannot/will not name the offshore 3d party service

Same as the op, switched from self-hosted to fastmail.

Try protonmail.com, zoho.com or fastmail.com

I've had decent results from Hetzner, although ymmv

No matter which provider you choose, your emails will be misclassified just because you're a new host sending email on the internet.

Over time, your server will build reputation by not sending spam and emails start to reach inboxes.

Most cloud providers block outbound smtp traffic