This is not how signature campaigns are working you need to be active and reach a minimum amount of posts every week/month in order to get paid.
If signature campaign owners wanted viral/spam threads they could easily create many of them and save many Bitcoins every month.
Yes, and i think the OP still don't understand about signature campaign on bitcointalk, i think the OP more suitable for joint on advertising website on internet although i am doubt there are people from bitcointalk who will use his service.
provably yes since his rank would surely not fit on advertisers want and also i think they want more reputable member to advertise their site since their business might in risk if their advertiser will do some lazy doings in this furom, thats why its advisable for OP is to find those signature campaign who's existing these days since that is the only campaign he can join with.and he must build some nice quality posting so he can be added faster on those good campaigns.