Try the untimed is my suggestion, with a rating range that is challenging but not oppressive. Give each problem up to three tries before manually going through the moves. If you want some time limit (maybe a few minutes per problem), use the timer included (it will count up on each problem).
Also note that learning often comes in jumps, I have had 200 point jumps (later dropped to +100) in rating playing 960 on another site, sometimes nothing seems to be happening then things somehow just come together, I suspect this will be the case if you use the tactics trainer untimed as suggested above for some length of time (a few months or so should do it, probably no more than 6 months).
I'm having a tactical nightmare.
In so many areas of chess, you can put the hours in and reap the rewards; endgame study and openings are the classical examples. The major thing I find with these is, once you've been shown where you went wrong, you remember for a very long time because the idea behind the move becomes engrained.
My tactical training feels very different. I can bang my head against tactics trainer for hours on end and still consitently make the same mistakes over and over again. I think a lot of this is due to the 'blitz' nature of the timer attached to the trainer (a whole separate argument on why it's too short could rage on for pages but please try to stay off this topic here), but another very strong reason why I feel this is occuring is because of a lack of strucutre in how the tactics are presented to you, and more probably, how I am trying to get better at tactics.
At present, I'm trying to do aorund 100 tactical problems a day on the site. On average, I score well on problems rated up to 1800, less well on 1800-1900, and find 1900+ hard in the given time frames. After a good few months like this, I see no improvement.
Tactics trainer on this website is my main source of tactical training. I really need some help to put together a decent and structured training strategy around this resource to help me improve. Any suggestions?