Connections probably are not your problem, it's how you set the resolution. I am far from an expert at setting up dual displays, and it took me over an hour to figure it out. First off you must clone the displays. I have a 50 inch Panasonic Viera Model TH-50PX80U plasma (2008 model). I had a quite a time trying to figure out how to get the picture sized right for both the 16X9 Acer monitor and my TV. I ended up with using 1360 X 768 resolution for both the monitor and TV. The image on the TV will be small unless you do the zoom feature, and then it fills out the screen completely. You also might try using a program called display fusion to set up your computer to TV as well.
https://www.displayfusion.com Also I run a separate audio cable to the TV and use the HDMI only for the video. I also have no idea of why a standard Sony DVD player would not work with the TV. Just make sure you using the proper input. ex: HDMI 1, HDMI 2, HDMI 3, etc.