Break the minute not having swam as a child

I'm 35 years old 175cm 64kg male self taught swimmer starting from zero 5 years ago. I swam laps for a while, but soon developed interest and passion in swimming fast over short distances and relentless daily practice. I have times in all strokes, but use freestyle as main benchmark. First time I tried to swim short course 100m freestyle I timed around 1:40. Over time this improved to 1:35, 1:27, 1:17 and reached a plateau there. So I went through a year or so of the Starting Strength program, deadlifted 100kg in sets of 5 and squatted 80kg. I began to feel like my body line, explosiveness, starts and push offs improved. Freestyle time didn't improve dramatically, only down to 1:15. At that point I felt I knew plenty about training of energy systems from Olbrecht, so I decided to only focus on improving my pure speed. I take 17 seconds for a push 25 in 18 strokes at 90-100 spm. I followed Boomer's Freestyle Reimagined and took my stroke apart 4 weeks ago. A stroke change is clearly going to take 4 months or years to happen, not 4 weeks, but I am beginning to lose the enjoyment. I am hugely motivated to see myself break the 15sec 25m and ultimately the freestyle minute, and have no idea whether it is possible with no youth swimming background. I posted on the UK Swimming Forum, but had no reply and thought I would post here too in search for tips or similar experiences. Would appreciate any comments! I've seen an adult successfully join an age group program, and haven't tried that myself. I swam with a masters club for 2 years, which was a lot of fun, but these seem to be geared towards fitness and training rather than focused development of speed. Moreover, I am not quite so fast and fit to join some of the higher profile clubs. I've been to see a number of coaches/swimmers for advice, including Swim Smooth, who all had valuable input, but nothing seemed to really point me towards some a big area of improvement. I feel like I might be missing an obvious one. There are definitely areas like "feel for water" and "stroke efficicency" that remain mystical to me despite having read volumes.