1.) Always follow the expert feeding chart. However, looks to me like this TA is just a repackaged GH flora Series. try using the GH flora Expert feeding chart with these nutes. Personally it looks like all hype to me I would change brands if i were you. just my opinion. GH flora series is proven over 2 decades, never heard of terra Aquatics.
2) I use 5000k in veg and move to 3500k when in flower. Plants love the 5000k in veg, nice tight nodes and compact green growth. flower loves the warmer 3500k for nice chunky flowers.
3) Yes Seaweed or kelp meal are one of the best nutrients out there. Did you know that there are only a few plants on the planet that use and store every element on the table, and kelp is one of them. Best natural source of every element on the planet, and growth hormones as well.