1, Pressure? Are you doing your statics in 10 feet of water? If not I think there's no pressure acting on you that will affect your times. The most probable reason for your reduced time in the water is the lack of relaxation.
2,
I doubt age has anything to do with your times. An average time is an average time, regardless of age. The average would be 3 or 4 mins. And you should not worry about your times so much. This might also be affecting your times because you're so fixated on results alone. Stop!
3, doing tables (whatever kind) are good for improvement. I suggest you continue doing so.
I'm sure you know this, but never train alone in the water. Make sure you have a buddy you can save you if you BO.
Keep up the good work.
