To get better at tactics, you need to do more tactics.
I've seen a lot of differing ideas on how many to do a day but I would think 5 may not be enough, though you also don't want to spend too much time either. I would say 15-30 minutes a day for sure, taking your time on each puzzle, not rushing them. If you can’t see the whole solution in 5 minutes, look up the answer, try to understand it and move on to the next one.
Part of tactical training is getting familiar with common patterns. You get that familiarity by seeing them over and over again in different positions.
I need a lot of improvement in this area. I do five Tactics Trainer problems every single day. If I miss one, I go into analysis mode and make sure I can do it in my head without moving pieces before I move to another problem.
What else should I do? I bought Chess Tactics for Students by Bain. Anything else? Right now I am turn-based 1375 but my tactics on Tactics Trainer are only in the 800s...slowly increasing every week...