My sweater shrank when it was washed. - Correct It may shrink if you wash it at a very high temperature. / It might become shrunken if you wash it at a very high temperature. My savings quickly shrank because I hadn't worked for a long time. (you mixed past with present perfect) My savings quickly shrank because I had been out of business for a long time.

My sweater shrank when it was washed.-correct It may be shrink if you wash it at a very high temperature. (wearing apparel) It may shrink if you wash it at a very high temperature. My savings quickly shrank because I've haven't worked for a long time. My savings quickly shrank because I haven't worked for a long time. My savings quickly shrank because I've been out of business for a long time.-correct