I know your pain. Undelivered emails kills you. Fortunately, I have resolved some issues since posting this question.
The first is noting the difference between sending on my desktop and through Outlook vs a campaign in IS. The major problem with sending on my desktop though Outlook was my hosting provider, Bluehost, has a very bad habit of not really stopping spammers on their “shared” IPs, thus, more reputable companies and web admins are often forced to just block entire IP ranges that are under Bluehost’s control. Bluehost is shitty enough to kindly offer you an “upgrade” to less dirty IPs, when really they should have been keeping the basic IPs clean in the first place.
I resolved this issue by routing all Outlook outgoing email through AuthSMTP. It’s a separate service, but they strictly monitor spam complaints, etc, and will happily send you packing if you bring down the IP reputation. I have considered and may still route all InfusionSoft campaign emails through AuthSMTP, but current events have slowed business, so I’m sending less emails at the moment. Pricing isn’t bad, with tiers as low as $36/year and 10K emails per month at only $180/year, most small businesses can probably work with that.
Now speaking only about items that might affect you InfusionSoft campaign emails, you definitely need DKIM set up if you don’t already. Please see the main DKIM set up help file, and Can someone please dumb down DKIM for me? for more technical details. DKIM verifies IS campaign emails as explicitly from your domain name, rather than being from name@infusionsoftmail.com on behalf of youremail@site.com.
So from your question, putting your gmail in the from field needs to stop. That can only hurt your deliverability. If you don’t have your own domain and your own email at your domain, get one. It’s not an option, you need it. Then set up DKIM. This will resolve a lot of deliverability issues. If undelivereds continue or are still too high for your tastes, your can try further methods like the AuthSMTP service mentioned above.