Structures on the bottom will not do much for reproduction improvement. Structures on the bottom are mostly larger fish attractors and not refuge areas for small fish. Small fish need dense habitat in shoreline areas. Reproduction improvement of BG & LMB are things that include shallow beach areas with pea gravel or small limestone No. 8's for spawning and nearby dense extensive structure are refuge, lounging, idle time areas. Structures should be in water 2ft to 4 ft deep as refuge areas for small fish. https://www.bobluskoutdoors.com/news-updates/nows-the-time-to-improve-habitat-2019-11-5168http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=514604#Post514604
To greatly improve the fishery a high protein pellet feeding program should be initiated. Something is eating the endless minnows and shiners - likely a few old larger LMB. Bald eagles are not eating the fish smaller than 4"-5". Bald eagles will also not be eating adult perch because the perch 'stay' deep and eagles harvest fish near the surface. The pond probably has more adult fish than you are able to see or catch.
IMO my experience the YP will not do very well with a strong reproducing BG population. Mainly due to too may BG competing for food. Plus without good predation the BG and YP will overpopulate that will result in food shortages, too many fish, and poor growth. IMO you should at this point be focusing on establishing a good pellet feeding program and proper predation and thinning of small fish numbers.