Back From A 45-Year Layoff--took a few days off...Question

So I joined Masters about 2-weeks ago...I am 61 years old...I essentially quit swimming in 1975 around age 16....so one year ago....I started swimming again....by myself...all freestyle...100-yard sets...first couple months I was doing 15 X 100s on the 2-minute....and I gradually increased numbers...to where recently, I was was swimming 30 or 40 X 100s, on the 2-minute...most of the time I was coming in at about 1:12 or 1:13, sometimes 1:15, then I'd have 45-second rest....then do it all over....my routine for the past 1-year would take me 60-80 minutes....plain jane, same thing everyday..... the last 100-yd of the set I would push myself, and I could usually come in under 1:05 So I joined Masters...the past 2 weeks I have been going to actual structured work-outs...a whole different ball game...wow..what a difference....I would like to enter a meet and swim the 100-yd Free and the 50-Free...off the wall I can now do 0:28 sec for a hard 50...but I need a lot of rest to recover....I can maintain 0:31 repetitive 50s...but I need time to recover because I was getting very short-of-breath quickly....yesterday afternoon, a coach noticed my breathing was off, and I was not exhaling until I started to turn my head out of the water, and thus I was not having time to take a full breath inhalation before my head would go back into the water....my breathing timing was obviously off...when I recognized this and began consciously exhaling earlier in my stroke this immediately helped my feeling of shortness of breath....it will take me awhile to unlearn my poor breathing technique that I likely repeated with all the 100s I have been doing....but I think I can get there I have 2 questions....(1) Does the current thinking and science on breathing technique for a Masters Swimmer (or any competitive swimmer) recommend that I should be fully exhaled while my face in in the water, or is it customary for a portion of the exhalation to still be occurring while my face is turned to the side and out of the water....(2) the Underwater Dolphin Kick (UDK) had not really been discovered when I was 12-16 years of age, and nobody used it...if my emphasis is to try and focus on the 50 and 100 free....can someone my age learn the UDK and use it to improve my times....I have not timed myself off the blocks on the 100-yd short course yet....but I think I am probably at 0:57 right now, just guessing....but my goal is to go under 0:56....my biological clock is ticking away...so I would like to get this accomplished... Could anyone who is an expert in Masters Swimming or Swimming in general and answer my two questions...(1) Should I be fully exhaled before my face comes out of the water (2) Can someone my age learn and use the UDK to improve my 50 and 100 Free times Please no smart aleck responses....I am new to all of this and I am sincere in my questions....everybody talks about the underwater dolphin kick (which did not exist back when I was swimming)....but I have seen a couple general posts on here where people say it does not help them and the flutter kick is the way to go