luckily my hands have not yet been ravaged by the cruel whims of time. but i am familiar with the problem of smart phone texting difficulties. similar to conchord, it is something that has actually reverted - one could write faster and more precisely on phones ten years ago. i actually dont like predictive text myself - i was around 15 when the first affordable pay as you go nokias came out, thus i sent messages for years without predictive text - and i absolutely, positively refuse to learn now. if you can find the settings option on your mobile phones, have a look for a message options sub-menu - that should contain predictive text options to disable at will.
would suggest to those struggling with touch screens to use a pointer of some sort - anything, a pen, matchstick.. whatever - to select the keys, slower yes, but more precise and therefore generally quicker
blackberry-type phones with the 'qwerty' keyboard physical keys (same as computer keyboard) are much easier to type with i find, anyhow