I'm glad to see this thread is still getting messages. I can't wait to go through them all thoroughly. In the meantime I thought I'd spitball some ideas.
Why not sell on BHW like
@Asif WILSON Khan mentioned? He is an Excutive VIP and I bet knows what he's talking about. There are over 8M users on BHW and all of them are interested in quality money-sites.
I would start to build an audience you could sell to. You can't link out from BHW but you can link back. Start a FB Page supported by a FB group. Pin your Page to your Group and market your group.
Create a Squeeze Page giving away a niche-related offer and collect emails while simultaneously autoresponding a linkout to your Group.
Use tools like Ninjablaster & Jarvee on a VPS to drive targeted social media traffic to your squeeze page. List some of your sites on the various marketplaces but in your sales description backlink to your SP. List sites, auctions, and listings with business brokerage classifieds like bizbuysell dot com [noaff]
Maybe even try to workout deals with brokers to access their lists. I'm sure some people on their lists don't want to fork over the dough for an established site. Buy those leads!
Do whatever you can to grow your own audience on FB/Email. Pay for adverts for your page. Juggle the traffic between website, email, page & group, and then list with BHW sending all that traffic to your BHW listing.
P. S. Advertise here. Run ads for $90 a week. Advert in a Sig... Even rent Sigs from Admins/Mods. Giveaway freebies. I think you can promote your listing here internally once every 72hrs. Offer a freebie thread and at the end of each day reply to all the messages in 1 post.
Make yourself independent from Flippa