You've solved the first problem with wrong column type. Let's solve the remaining one (with dots). Recall that there are 4 columns with wrong types left ('morgh', 'valueh', 'grosrth', 'omphtotinch'). These columns considered to have dots as indicators for 'Not applicable'. For instance, columns valueh and grosrth are mutually exclusive, since the first one indicates the price of dwelling (i.e., house is owned) and the second one indicates the monthly rent.

The most appropriate way to solve this problem is to replace dots by NA values. In that case, we would be able to manipulate column like a numerical one.