Mailchimp newsletter campaign. First of several

I run a small drone services business - about to release our new showreel via Mailchimp newsletter, to a database of leads and existing clients. So I'm mostly B2B.
I already have the databased exported (spend prob 100 hrs cleaning up my CRM over lockdown), and I have a rough draft for the email copy.
I'm pretty rusty with Mailchimp (haven't done a newsletter since mid '18) and don't want my lack of skills here to jeopardise open & click rates.
So what I need are:
- solid import to Mailchimp (fixing current account conflict with my existing 'audience' - only allowed 1 on my free account)
- Ensure good first/last name split
- Guidance on compelling subject line
- Advice on refinements for newsletter copy
- Engaging template (my current one may be fine, it is here: https://mailchi.mp/520b707b6a12/qf0ukn1jkt )
- Guidance on send results and how to act on the data

Please let me know your thoughts, and availability over the next week or so.
Thanks
Chris