Fatheads will not use the brush effectively for spawning; logs will be more useful. Fatheads ideally need a flattened surface; the larger the more room for egg deposition. Sometimes egg masses can be 3" to 5" around.
Adult shiners will aggressively eat fish fry. Number of adults stocked will determine impact on fathead production.
Two to five pounds of fatheads in 1/3 acre will produce more fatheads then you will get harvested. Breeder sized fatheads run about 150 to 250 per pound (2"-2.5"). If you stock too many breeders you will have poor growth and have way too many tiny (1") fish at harvest time. The first year I would stock fewer numbers and learn what the pond will produce. Are you going to fertilize or feed ground pellets?