It's meant to rip right off. Pourable silicones were designed to temporarily protect fragile printed circuit boards from handling. If they are squeezed between something tightly they'll retain their shape; but they don't have adhesive properties like thicker RTV silicones do. There was an entirely different kind of clear liquid sealant I used for hermetic bonding; but it was way too messy for any optical usage. But being retired, I'm not in the sealants business anymore, so might be a little behind what's currently available. At one time, I was given free samples of all kinds of things, and dedicated aerospace and tech suppliers were in this area too.
I did a LOT of experimenting, fully expecting that many would be bellyflops; but sometimes that's the only way you learn the truth about a product. But you have to watch what happens over years or even decades in certain cases. No serious industrial products ever come with time warranties, just with hard engineering specs. "Lifetime warranties" on sealants are total BS marketing and almost universally related to the cheapest goods. You have to read the fine print. Of course, I was doing all that testing not only for sake or personal usage, but because clients depended on me for competent non-BS advice; and at that time we held one of the largest selections of sealants around. It was only part of my job; I handled all kinds of other specialized product lines too. Had a big military, marine, architectural, and industrial customer base, so my employers were fully supportive of all my experimenting, even if it was for personal ends. Serious artists were in that mix too, even big photo labs.
Molding silicones and medical silicones are entirely different categories. I don't think they would be of interest to you. My wife worked in plastic surgery for about 8 yrs, which certainly has legitimate applications, and she was excellent at both stitching and certain kinds of diagnosis. But she got disgusted with the greed of some of the practitioners and moved on. These were all highly licensed real surgeons; but you've no doubt heard about fake ones too, who injected ordinary hardware store silicone into patients and turned them into looking and feeling like monsters once that broke apart in their bodies.
At times, it's really hard to know what's going on between a particular medium and an immersive sealant. I got involved with it in relation to the big Cibachromes I was making at the time, and had my own proprietary method of encapsulation which provided an exceptionally nice visual presentation. That was prior to today's thin permanent adhesive foils. I have gear for that too. But sometime back then, pourable potting solutions started being used within acrylic shells for Cibachrome. And the fact that oxygen was sealed out apparently greatly reduced the fading rate. But the fact that those were routinely installed under horribly high-UV projector lighting, popular in high-end venues at that time, resulted in a torture tradeoff hard to objectively analyze. But the process itself was ridiculously expensive and tricky.
There are just too many variables. I actually sold the sealants used to cement the correction lenses of the Hubble space telescope into their mounts, involving a product which would perform badly here, but apparently worked wonderfully in the oxygen-free vacuum of space. I didn't predict that - I just sold the stuff to them, according to their own specification. They were routine customers anyway. I won't mention what that was, cause it's fun to guess, being something improbable. They're still in the mega-telescope business, just ten minutes up the highway in a big unmarked building.
Enviro consequences? True "rubber-based" sealants are often self-curing and only outgas a little. Some are moisture-curing, absorbing humidity. After outgassing, these products tend to remain inert. But health consequences applying them all depends. That is what MSDS sheets are for. And how they finally break apart, and then potentially get into streams and so forth is more a topic for proper landfill assessment. Their relation to window manufacture and installation is a complex topic; but we were especially involved in that. And in that case too, an ideal sealant would remain watertight in fashion of a gasket material, but not so aggressively that it was not removable by some mechanical means (specialized equipment we both used and sold). Hope this is ample food for thought, so far. Good luck!