There are many ATMs in the market of Leh. There some ATMs of the State Bank of India where the Tibetans have set up their refugee camps. Cards are not accepted in all places so it is better to carry enough funds with you.
Prepaid mobile connections does not work there. So, it is better if you carry a postpaid mobile connection before venturing out there. Sometimes you may not get signals there specially while you are out for your sightseeing. You get the PCO booths in the market from where you could make your emergency calls.
Wifi connection is available in some hotels and cafes. But the connections are very slow and are of very poor quality. If you are really in a need to use wifi then you may use so.
Drinking is not prohibited there. But due to the consumption of the liquor it might cause dehydration which may lead to headaches and nausea there.
You may tip at the restaurants depending upon your bill or according to your wish. You may also tip the drivers depending upon the length you have travelled.
Kerala has no such records of major crime with the tourists. But it is always advisable to be very cautious about your belongings and not to visit isolated places.