I think this is a good idea, hopefully it will improve traffic here.
1) Skipping the narrative will shorten the level of effort so I agree with you here.
2) Short play - just get it out there, if there is enough interest you could always circle back and do a long play later. Again, lower level of effort.
3) I think both is a good idea. If someone gets to the point of wanting to download a game they just checked out in a walkthrough, chances are that they would like one of the other games available.
I assume this will be limited to games that are worth playing through? Complete, non-demo, winnable?