If you do a search for Ram HVAC doors you will find more info that you care to read. Basically, Dodge used a crappy HVAC switching system in these trucks that usually leads to airflow control doors breaking and causing part of the system not to operate properly.
In your truck, mode door 1 directs the airflow either to the main front vents or into the secondary part of the system. If air is coming into the secondary part of the system, mode door 2 directs it either to the defrost or to the floor. If you have no airflow to your feet, it is very likely that your mode door 2 is broken. This is very common and when it breaks, it falls down and any air sent into the secondary part of the system will be sent up to the defrost. This is the most difficult door of all of them to repair and involves tearing out a significant portion of the dash. If you are serious about repairing it, you should check out this link. They offer a good product and there is some good detailed info and videos on their site.
As for the slow change from defrost to the main vents....that is normal to an extent. It takes a little time for mode door 1 to move from one position to another to redirect the airflow but it should be taking seconds, not minutes. If it truly is taking that long, this could be a sign that you may have future issues with mode door 1. It doesn't really sound like it's broken because when they break, they basically stick in one setting or another. Could be that the little electronic motor that moves the door is weak and is moving slowly taking extra time to change the position of the door.
Hope this helps and good luck!