hello,
yes i have had problems with s70/old v70 ign switches before and this could cause the loss of electrical power you describe,there may be another cause for your problems but it would be a big conincidence,start with the ign lock problem first and see if that cures it.
you can buy the lock barrel precut for the key and the switch that goes on the back of it as seperate parts and i would recomend getting them both as even though its probably just a faulty barrel (causing the lock to spin around) often the contacts in the switch get burnt out as well.

steve.