Congrats on the progress. It's stuff like that that keeps me motivated. If your goal is building muscle then 2-3 30 min bouts of cardio will do you good a week. I do mine after my workout if I still have energy or I hit it later in the day. Some believe while cadio has its benefits it isn't truly needed unless you are cutting and trying for single digit bf. When building muscle you will gain fat which is why people try to lean bulk which means as little fat as possible. Cardio now would help you keep the fat increase minimal. In most cases you either build muscle and some fat or burn fat while maintaining muscle although with the right diet and routine you can build muscle and burn fat but it's harder. You can work abs 2-3 times a week and it really doesn't matter when or what muscle groups to be honest. If you really want that 6 pack and build muscle then calculate your macros if you haven't already. Good nutrition and a solid routine is what you need. You can even bulk for muscle gain during the winter and cut for low bf during the summer which I believe many like to do.