Hi Im Scott
Your rear seats should have a button release on top of the seat back it will either be a button, a lever or a raised pole. Once this is depressed (or pulled) the rear seat back will fold down and allow you access to the trunk area. The (usually) yellow handle will then be located where you are saying the seat release is. I am thinking that you have this mixed up with the trunk release handle.
Hi I have just looked through my notes
You are 100% correct there is no way of folding down the rear seat without gaining access to the trunk. Just another one of those "intelectual" designs we sometimes encounter. Okay
You already have the rear seat bases folded away, so you should be able to gain access to the lower seat back mounts (they will be located under the rear seat backs, each will have a bolt holding them in) you will need to remove these bolts. This should then enable you to raise the lower ends of the seat backs. once you have raised the lower ends the seat backs will either come away from the top latches which hold them in or will pivot up enabling you to crawl into the trunk area to manually release the trunk lid. The manual release located in the centre near the lock and will be glowing. Be sure not to close the lid again until you have gained easy access trough the rear seats
I assumed when helping you through the 2nd part of your question I was addressing the 1st part also. Due to the fact that you can hear the trunk lock attempting to work when you operate the interior release and remote this tells me that there is no problem with that side of the mechanism. The problem lies with the lock assembly itself. for some reason it has jammed or failed and the only way to release it is either with the emergency release inside the trunk or with the key which is damaged. Perhaps the damage to the key entry is the reason why the lock will not operate normally using the remote or the inside release mechanism.