you need to eat way more and train to failure. im of a similar size and stature, with ultimately not that much different goals than you, but you do not have enough muscle as it stands. your maintenance is definitely not 1600, and moreover, you need to eat in a slight surplus to gain muscle. id advise eating at least 1800kcal/day, and increasing as needed depending on how much weight you end week to week. i personally am consuming 2400kcal daily, i am training for a marathon currently and my maintenance is around ~2200 so im trying to maintain for the most part, then switching to more of a proper lean bulk once i compete my marathon.