Welcome to the the forums, DanDaMan! You are on the right course for your training. I myself do very much the same routine that you are for training.
You will find that 90 seconds isn't great, but isn't bad either. The one thing to remember is that developing longer breath holds takes work and the improvements comes gradually. The base work that you are doing for your cardiovascular efficiency will pay off down the road.
I myself also make use of the
Powerlung, which is basically a breath resistance device. It has helped me improve my overall breathing and to an extent, my static apnea times. You will find though that if you are working to increase your dynamic apnea, where you are swimming underwater, that you will need to continue doing all of the above. A variation on your weight lifting would be to add sessions where you hold your breath while lifting - this will cause your body to adapt to working under load and with limited oxygen in your system. The adaptation will markedly improve your dynamic apnea times.
I personally do not work too much on static apnea, as I personally feel that it doesn't represent the true nature of the sport.
Others might feel differently, and that's ok, this is just my opinion.
So press onwards and let others know how you are progressing in your training.
