wp-list-table question

I have been learning wp-list-table for the purpose of creating a wp-admin-style table for my application. I followed this example, finally a table was created with my data records (from a remote database). However, I have had a few issues which I like to hear advice from people on this forum.

1. My table does not show little triangles on sortable columns. It only highlights the column title;
2. The table shows two (orange) rectangle blocks in 1st and 2nd column (I made the 2nd column as the primary column in setting
$this->_column_headers);
3. The actions for the first column always show on the screen, rather than only shown when the cursor is hovering on the value of the column.
4. Hidden columns does not seem to work.

Here is a screenshot of how does my table look.

Any advice and/or suggestion will be greatly appreciated