Question to Coaches - Endurance

Question to Coaches - EnduranceHopefully I won't lose anyone here, this might get long winded as I try to "build" my question. I am 50 years old and have gotten back into competitive swimming after a 30+ year layoff. Initially my local YMCA offered a masters swim practice in the evening, due to what the YMCA considered "low" participation this practice was scrapped so now for the past 2 years I pull my workouts off the forum pages and train solo.... Occasionally I can participate in the afternoon practice that is still offered and get some feedback from the masters coach....he is also the age group coach for the YMCA swim team. Over the past two years I have competed in 1 mile open water swims with decent results and times. This year (2015) I have competed in two "low" key swim meets in an attempt to see where I am and how much more improvement I still need to be competitive. My first meet I swam 200 free(2:16.45), 200 IM(2:31.22) and 100 ***(1:18.18)...all times are for yards...this past weekend I swam my second meet swimming 200 free(2:13.) and 200 IM(2:26)...while I feel good about lowering my times I was realized a few things....mainly my endurance isn't there. In the 200 free I was even or ahead at the 100 but destroyed on the second 100, in the IM I was ahead until the 125 mark....subsequently fell behind anywhere from 5 - 10 seconds approximately.... As I see it my endurance level leaves me gased to the point I can't keep up...and admittedly my kick could use some work as well....My typical week of practice is 6,000 - 9,000 yards depending on work schedule along with a few cardio classes and some strength training. How can I build my endurance up so I be more competitive...my goal is to be at 2:00 minutes or lower in 200 free and sub 2:15 for 200 IM....other motivation is the USMS Spring National Championships next year in Greensboro, NC. Thanks in advance for your input and suggestions! Tim Johnson Lynchburg, VA.