Would it be useful to spend some time sending energy with Sword Fingers to my kidneys? Could I spend much longer periods doing the kidney massage and the tailbone tapping?
You can do either of these. Of course, remember to 'heal *with* the Universe' rather than from the perspective of 'trying to heal it by yourself'
There is also a powerful qigong exercise for kidneys i have learnt elsewhere, but i am apprehensive about mixing systems. Perhaps I could do it a few hours either side of SFQ?
Sure, just keep a bit of 'time' in between the exercises. Also, it would be very helpful to Self Concentration and Small Universe in the evening, if you can. (one after another if you have the time) These will assist you further with exponential results.
Also, the Kidney and Liver imbalances you are experiencing seem to be perpetuating one-another (perpetuate means to continuously cycle) Liver energy can become stagnant from excess anger or irritation or other 'heated emotions' and Kidneys can become deficient from fear, worry, etc. Spending alot of time worrying about a problem, often makes it worse. It may seem dire, but fortunately, we can solve this actually pretty easily.
The heart is a balance factor between the liver and kidneys, as well as the rest of the body. Spend a few minutes feeling 'good feelings outward' or feeling loving, and you'll notice how quickly either fear/worry, or agitation both diminish.
The Universe accepts emotions and feelings 'as gifts' from you. It takes these and multiplies them and returns them to you based on what they are. Make the intention to feel wonderful as you connect with the Universe in meditation, thank the Universe and your Source for you healing (even if it seems in linear time, that it hasn't happened yet) and your positive feelings will ripple outwards into the Universe, and return to you.
Don't concern yourself with the 'past' or mistakes you seem to have made that led you to this state. Maybe you are in this state so that you will master healing and help someone else who is even 'worse off' than you are now, and by being able to overcome this, you will effectively help them--more than you would've if you hadn't 'had to learn it'
Also, a useful herb worth checking into is Ginkgo Biloba.
I take this every day, it is an anti-oxidant, it expands blood vessels(allowing more oxygen to reach organs) and helps remove negative energy in the body, it even helps with aging and memory problems. It will help with liver, kidney, heart, intestines,...actually everything.
I *highly* recommend acquiring this. In the US, it should be around 9-15$ at walmart in the herbals and vitamins isle--depending on size of the bottle, etc. It can be taken with any medication and/or other herbs without effecting their function (in fact, it'll probably help them work even better) Of course, you don't have to take my word for it, look them up for yourself, try em at least once and see how they work for you.
Oh, and a little extra vitamin C--might go a long way.

~Z