When I double seal, I put the bag as far into the machine as I can, then vac seal. Then I pull the bag out a little bit, then hit the "seal only".
The FoodSavers are probably overpriced, but many people on this forum use them and have fine luck with them. I have a VacMaster Pro140. The model is no longer available. It is similar to their Pro110, but more powerful. The Pro140 retailed for about $150, but I got it when they were selling out of the model on sale for $79. I don't think the Pro110 would be an upgrade from your FoodSaver. And the next higher model VacMaster is about $300. You might want to get suggestions from people who have Westons. My dream would be to get a chamber sealer, so I could seal liquids. But they start around $600-$700 for a basic model.