regarding your first question,see Berachos 55a,Sefer Chassidim 920,and Kaf Hachaim 167:41 which say that a table is like a mizbeach and one should careful not to kill a louse on it this includes a table which one learns on as well.
Second question,the Be’er Moshe talks about it ,this q has been answered more than once on this site,do a search.