Sending email via SES without SMTP

Yes, you can send email using a key/secret for an iam user rather than via the smtp.

Here are sample policy permissions:
https://docs.aws.amazon.com/ses/latest/dg/control-user-access.html.

And here is the api/cli reference, different language references are linked at the bottom:
https://docs.aws.amazon.com/ses/latest/APIReference/API_SendEmail.html

I've never tried setting the source ip condition for sending email in a policy, but i'm not aware of any reason why it shouldn't work. Example permissions are here:
https://aws.amazon.com/premiumsupport/knowledge-center/iam-restrict-calls-ip-addresses/