Coming back to where I began

I just started back swimming after 15 years of abusing my body and have began to feel at home again in the water and want to keep it that way, i also just joined the masters for the free monthly magazine :laugh2:. I have 2 kids and work so time is pretty slim but I have managed to find about 3 days a week where I can get 45 minutes in at the Y. After 3 months though I am starting to want to spice up my workout a little and am open to suggestions. The following is not a brag session and hope it is not taken that way, I just know that you can't give good advice to someone that you don't know any background or goals for, everything is short course yards. Swam all the way through senior year in HS and was always in USS from 10 yr old to the end. came from a program that believed more lengths = better swimmers so we did a lot of boring sets and not a lot of specific training so I don't have much background in ascending descending, mixing and matching sets (think 8-500s on the 6 min, I avg'd 5:12 my senior year on this set). I was a distance freestyler because that is where my coach needed the most help and honestly fast twitch muscle fibers are not something i have in excess. But I do have a good backstroke and OK fly, *** stroke hurts my knee (fractured right inner chondile in 9th grade) so I either kick light or fly kick it. I was a workout fiend and loved to try to break the pain barrier whenever I could. Hit a plateau though around sophomore year, went 4:52 in practice but only went 4:45 at state meet, senior year got down to 4:44. 100 free time was just under 50 sec and was a 1:45 in the 200. Our typical in season day consisted of 3k in the am and 8-10k at night. Fast forward to today. I hit the pool about 3 times a week and might try to start making it 4. I have 45 minute windows only right now so workouts need to be able to fall in that window, I can get 2500 in that time depending on sets. I "think" I would break 6min in a race setting 500 right now but would rather be training more for back/IM/200 free and just for overall getting in good shape and have the swimmer build again. Couple sets I have done lately besides 500 swim/kick/pull followed by some misc stuff for another 500-1k yards Stroke 500 warmup with/without kick pull 6-50s fly/bk/br 5 sec rest 3-100s IM 10 sec rest 2-150s Fly/fr/bk/fr/br/fr 10 sec rest 3-100s IM 10 sec rest 6-50s fly,bk,br repeat 5 sec rest 200 easy 600 warmup 6x100s bilat breathe hard 10 sec rest 6x50s Kick 3 pull 3 10 sec rest 6x25s sprint 5 sec rest 200 cooldown