and for that last question...No ..you wont be able to just move the card and go. the reason is that sup engine is going to be changing slots from 1 to 3 . Also its a chassis model change and in my experience its better to have a new configuration in ...

im pretty sure that fan speed is dictated by temperature ..not load. you need to factor in the air temperature coming into the swtich as well. A switch with 5 percent load but sucking in 150 degree air will shut down a lot quicker than a switch at 90...

The guide to setting up redundancy is here: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/01xo/configuration/guide/config/RPR.html

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-4500-series-switches/data_sheet_c78-612364.html Its listed as supported in every 4500e chassis

If its possible can you send me a copy of show tech from a working AP and a non working AP? I can do a quick look over it and see if there is something missing.