Actually, Rashi had access to more Medrashim than we do. Keep in mind that many Sefarim were lost when they were burned in france. Also, Rashi didn’t depend on what was in his local library. He travelled alot. I found Rashi using a Russian word to explain a Pasuk, and Polish too. You can’t just dismiss a Rashi off hand, even if it doesn’t fit your fancy. Before wondering how Yitzchack was able to marry her, did you stop to think that no one in her family objected on the grounds of her age? They asked her and valued her position.
The Meinekes is probably her caretaker.
We must realize that although you can find that a Rishon wasn’t privy to certain information, like text or science, what he writes is Torah. In other words, when you find a piece written about the four elements, although these are not considered anymore to be the elementary basics of matter, we learn and revere what he writes. If a Tzadick were to pass a painting, and he would comment on it and point out rome great idea that we can learn from that piece of art, we listen to what he says, which is truth, but we don’t delve into that artwork. So the Rishonim utilize the current science for purposes of Torah, and we learn and internalize that Torah, because it is Torah Leshma and written with Ruach Hakodesh.
Tosfos says that the Medrashim argue on this. How to reconcile that with Eilu Va’eilu is a different topic. However, we don’t pick sides, we learn all of them because they are all Torah.