The boot release sticking is corrosion between sides of plastic handle and the bracket it pivots in. As advised spray some decent lubricant ( not WD40, I did say decent lubricant, maybe 3in1 with PTFE) you will need to work the handle quite a few times until either the rust wears away the plastic handle or the lubricant does its job, a quick spray every couple of months on the hinges of the handle should keep it sweet.
Doubt engine noise is specifically coming in through vents, but it may be induction noise, check if the engine air filter is present and in good order, also check cabin filter.