I also share a hate for DLink products. I cringe when I get into working with a customer who wants to go VOIP and the closets are full of cheap DLink switches or other budget models. For that reason, I have no personal experience with thier home product line so I can't truly comment on the home line. However, my thoughts are that if they won't spend the R&D to make reliable business models, how could I expect them to be better on the residential line.
I'm also puzzled on the 2nd question. I assume you must have a cable modem from your ISP. Unfortunately my company lives in the fiber and copper world. Cable is the enemy. heheh. I haven't done networking on coax since my school daze where there was still,among other things, an aging VAX VMS network on token ring. Yup, I'm old.
Generally though, you would not 'normally' consider networking your house via coax. Also, you would not normally try to split your ISP's feed ahead of the modem and run two modems/routers. It may or not be technically possible but I doubt very much your ISP would support splitting it ahead of their supplied modem.
If that is what you mean, instead do as others have suggested. Buy a small Ethernet switch and then run Cat5 or 6 to everywhere you need a connection in your house. Wireless is indeed also a much improved option these days as well.
I'm Riffing. People usually stop me when I'm riffing. Or carry on without me. That's also an option.