I think the number of voters you're talking about, who don't already hate Democrats but for whom a pro-choice candidate is a deal breaker, is literally in the single thousands nationwide.
For issues where it would make electoral sense to run candidates who deviate from the more-established party standard, guns and tariffs/trade are much richer veins to tap, and easier to run on. It's entirely possible to run a pro-gun and pro-gun regulation campaign that embraces the responsibility that should come with gun ownership, just as it's possible to run as generally pro trade, but supportive of specific protections for important industries. The first could help secure a lot of the type of voter you're thinking of, who I think are mostly conservative-raised young men in red states who are educated and have drifted away from the GOP on other cultural issues (I don't know if there are actually electorally significant numbers of people like this, but anecdotally I feel like I know a lot). The second is more of a rearguard action protecting against the likeliest defectors. Unions praising Trump's tariffs are a problem for us and to get some of the unionized work force back on side we're going to have to do some "guys we can actually do effective protectionism for you without blowing up the fucking economy" messaging.
But Bozo is right, policies are not nearly as important in elections as guys like Klein want to think they are. Candidate charisma matters far and away more than anything else. And 956 was right in that it helps if the candidate comes across as if they like the people whose votes they're asking for. That's why Beto came close in 2018, it's why Beshear wins, and it's why AOC and Zohran are so popular. Clinton never seemed like she liked anybody at all and Kamala felt too reserved and guided by polling in the typical Democrat politician ways. Those were bigger problems than ideological purity tests.