sorry for my late answer.
1) This is possible. The price search is not "live". It's cached and refreshed in the background.
You can use the ean of a product for a automatic price comparision, but you can also define the offers manual.
2) There is a feature "list" available. For this you can define a keyword. The parameters are depending on the api you use. For amazon and ebay you can filter the price. Most of the other apis only support keywords.
3) The price is not "locked". It's always the current price - 70%.