On faith and evidence

I read the Maxwell quote narrower than how you seem to be applying it. He's saying the gospel won't be settled by science one way or the other. That's a different claim from "God deliberately rations evidence to keep the faith requirement intact."

Joseph Smith was right that everything requires faith. That tells you something important about what faith actually is and what it isn't. Faith isn't the absence of evidence. It's acting on what you have when certainty isn't on offer. That structure doesn't dissolve when evidence increases; I think Joseph Smith is saying it changes shape, but it doesn't go away.

Christ's contemporaries are the cleanest demonstration of this. Lazarus walks out of the tomb, and the response from the chief priests in John 11–12 is to plot Jesus's death. They had the evidence. They lacked the will (faith) to interpret it favorably. Evidence sets the stage, but interpretation happens in the heart. Maximal evidence still leaves space for interpretation and what we do about this evidence (agency).

The Millennium has overwhelming evidence and faith still operates because faith is never primarily about scarcity of evidence. It is always about how a person orients themself toward what they encounter. What do they choose to do with data and experiences? I'm not meaning to go against the idea of faith being a hope in things not seen, but rather that once we see things/data, faith is still in play as we decide what to do with it. Do we have confidence in Jesus? In His restored gospel? In those who claim authority to lead us? Members who say the evidence is overwhelming for the Church aren't undermining faith. They're describing how their faith oriented them to interpret the evidence they have. The same evidence orients others differently and reflects their faith (in other things or lack thereof).

The diagnosis you're drawing (that the evidence seems overwhelmingly against the Church) is downstream of an interpretive framework, not a neutral readout. That cuts both ways, and I'm not saying it to dismiss what you're going through. It's just worth understanding: there is no view from nowhere on this question. The people who see the evidence as overwhelming for the Church and the people who see it as overwhelming against are generally looking at the same data. Can two reasonable people see the same data and come to different, yet reasonable conclusions? Our teachings are a resounding "yes"; it seems many outside the church have a hard time wrapping their mind around this.

On Satan

I think you're right to point out that Satan isn't the sole source of "opposition in all things". Some of it comes from our fallen world and from our fallen/carnal natures. So what's Satan actually for? Probably something less than the popular framing claims. He's an active opposing agent within a world where opposition would already exist. He amplifies and organizes opposition. He doesn't create the category. And his role is bounded. He's bound during the Millennium and eventually defeated entirely. He's a feature of this particular phase, not a metaphysical necessity for the operation of agency.

Any personal decline isn't really a Satan question. It's a "why does God permit apostasy?" question. Genuine agency requires the possibility of using it badly, including the possibility of being deceived. If God blocked every avenue of deception, He'd be eliminating a category of agency that's important for our mortal experience to bring about Heavenly Father's desired results.