yeah i have that issue where i cant find something to play sometimes cause I have too much lol

If you've been to the chrono forums, you'd see that other users either gift or trade games to each other, sometimes even a mod does that. So I don't think linking a steam account would be on their to do list.

Steam level 25 seems a bit high. I'm only level 17.

Pretty good suggestions... in theory. Sadly, they're very easy to abuse in practice.

minimum steam level 25

Free badges are more than enough to reach a decent level: community badge + events from the past 3-4 years = level 20.
Add to that the years of service badge and the games owned badge, and you can easily fill in the gap with random trash.
Pretty easy with older accounts, especially the kind that are used to farm lots of shovelware collected from shady giveaway sites.

minimum 100$ spent on steam account excluding any bundled games

That's the same as Steam Gifts.
Just take a look around the site and see how well it works in keeping out undesired users (i.e. bots and alts, but also random opportunists who slip through in the short time window before games get bundle listed).

ip check

Dynamic IPs. VPNs. Proxies. Whatever floats your boat. In any case, circumventing it is child's play.
If you ever visited any medium/big Discord server (i.e. the kind where you sometimes need to ban people), not necessarily on the moderation team's side, you'll know how resilient some people can be.

allow redeeming keys only through the site to the linked steam account

Direct key activation would be effective, though only mildly, as given the demographics that should be supposed to fight, I wouldn't underestimate their greed (you'd probably be surprised to see how far they're willing to go for profits).
Not to mention the backlash such an action would receive, which I doubt they -or anybody, really- would be willing to face.

Not sure if that'd be too effective, sure it'll reduce mass exploiting but it won't solve it, only piss off legitimate users.
Steam level is pointless, one of my alts is over level 25 and I only use them to farm cards. Meanwhile a bunch of real users don't bother with levels and are barelly over lvl 10 despite using steam for years.
Almost everyone has access to at least 2 IPs nowadays (house conection + mobile), and VPNs and proxies are widely used.
If you only allow activating the keys to the linked account gifting won't be possible anymore, I fail to see why would you stop that or how would it help.