Question about how wet najāsah transfers (please advise, assalamu alaikum)

Assalamu alaikum. I’m asking because I want clarity, not to be obsessive, so please be gentle with replies. If you have severe waswas or can’t handle detailed fiqh discussion, please skip this post. Otherwise I need some practical guidance and sources. I’m looking for a clear explanation of how wet impurities (najāsah) transfer. I know the basic idea that wet impurity only transfers through wetness, but I’m confused about two things: 1) how far or to what degree it can transfer, and 2) what exactly counts as “wet” or “damp.” Example: a newborn soils their clothes and the impurity gets to the outer layer of garments. You can see the affected area and can barely feel a difference by touch. If someone touches that spot, does impurity transfer to their hand? Or does transfer require clear visible wetness of the impurity? If the hand does become impure, can it then pass the impurity on to something else - for instance, if the person’s hands are sweaty? What level of sweat counts: actual beads of sweat, or is skin that just feels slightly moist enough to transmit it? I’ve looked online but most explanations are contradictory or give only extreme examples, which doesn’t help with these borderline everyday cases. I’m not looking for people to dismiss this as waswas; I want reliable fiqh sources, concise rulings, and practical tips for preventing spread of impurity in normal family situations (especially with infants). JazakAllahu khairan for any clear answers or references to madhhab opinions or trusted fatawa.