1. Why is age an issue for Biden but not Trump? It makes no sense. I'm not saying you are wrong on that being an issue, it is just a manufactured concern because if age were the issue, then Trump, Grassley, McConnell, Feinstein, and probably a dozen other people should be unelectable as well.
2. The abortion issue has single handily flipped around a half dozen special elections since Roe v. Wade was overturned. You better believe you are going to see ads with Republicans saying how they want a national ban on abortion about every 10 minutes starting in July next summer. Several states are putting women's right's protection policies on the ballot next fall for the express purpose of bringing people out to the voting booth (and protecting women's choices over their bodies, of course). That's what the entire purpose behind the Republican attempt to change the policy adopting rules in Ohio last summer. I can't disagree with you more than I do right here. The evidence just doesn't support that people won't come out to vote on this issue by itself.
3. This one is kind of silly. No President is an expert in everything. That's why they appoint experts who are the best in their field and then listen to their advice. So, the question shouldn't be "Does Biden understand this?" The question should be, "Who is Biden going to appoint to be an advisor and who is he listening to make decisions on?" People need to compare who will be advising Biden vs. who will be advising pretty much any GOP candidate. Which ones are more likely to be compromised? And before you let Hannity and Tucker answer that question for you, keep in mind the people Biden has appointed right now are not raping the US treasury instead of doing their jobs. Something that was common policy for many (most?) people Trump put in a position.