I would agree that you should give your top choice , Bowdoin, your best shot with ED2. I think you need to know the outcome even if it turns out to be be negative You already have a few acceptances in the bag and your RD list is reasonably sound. So I would stop over-analyzing and go with your gut.
I would also agree that your disappointing outcome at Middlebury will not necessary preclude the same outcome at other selectives. In other words, as long as you have reasonable less selectives in your mix, there’s no reason not to include other reaches for both ED2 and RD.
Based on your profile and wishlist I would suggest you add Williams to your RD list. Williams like other New England LACs, admits heavily on fit and your academic interests (both STEM + writing intensive) and your outdoorsy ECs seem to be a good fit. Plus its strong “ski culture and easy access to ski slopes”.
Cornell? I don’t know. Despite its lively town within a rural setting, the culture seems to be on the opposite side of the scale from the LACs that you favor.