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1. Don't worry about back-button scripts until you're in profit and doing volume.
2. Don't worry about it, I get these also.
3. Start with 2-3 offers (ideally in top offer reports from networks)
4. Focus on SOI, you can still get a healthy EPC without the need for a massive budget.
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How much actual traffic to the landers???
I dont understand one thing, please be more specific here :
Do you rotate 7 landing pages and send the traffic randomly to all the offers? Or you created some funnels? Are all those landers following the same logic and are they related to the offers or is it some kind of a mix? I mean, in case you have different angles on the offers, promoting different offers that dont match the angle ... thats quite a mess and you shouldnt be doing it that way 
You also mixed pin submit and SOI offers, thats also not the best idea as you need carrier traffic for PIN submits and SOI can work well on WIFI too.
I need more info from you 
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Other than that, you can do the same steps as with any LP. Try to put some flashy elements on top of the page. Large eye-catching headline - whatever eye catching actually. Experiment with the window size, test if it loads properly with all device types you are targeting. Try sound, experiment with font types and size etc ...
If you have a funnel good enough, it can work with redirects too. Its just about finding the good sources and keep the prices low enough
You could run your LP's through pingdom/GTmetrix/webpagetest.org to test load times and try to optimize them to reduce loading speed in an effort to increase CTR.
Also, with the back button redirect, you can set up a separate campaign and run your redirects through this. That way you don't skew your actual CTR from your main campaign.