Yes, bases can be combined as you wish. You can add vit E, but since soap is a wash off product, I feel that it would be wasted. I would not add cold cream as you could loose bubbles. As far as adding oil to the base I use 1 TBS. per lb. of base. For books try Melt & Pour Soapmaking by Marie Browning, Making Soaps by Paola Romanelli, Soap Making 101 by Debbie Rodgers or Making Transparent Soap by Catherine Failor. BrambleBerry also has soap books on their web site>
http://www.brambleberry.com/Soap-C153.aspx