1. The show/hide add to cart checkbox in the cart admin settings is meant for people who only want to use the cart as a product catalog and not allow checkout. If you want to hide the add to cart on the product list page you can set the visible property to false in productlist.ascx as follows:
<asp:ImageButton ID="ibAddToCart" runat="server" OnClick="btnAddBasket_Click" ImageUrl="~/DesktopModules/Smith.BuyNow/images/add_to_cart2.gif" Visible=false />
2. Regarding displaying product information/pricing next to the product to fill up the blank space you can modify the productlist.ascx page to format the product layout any way you like. The product listing layout uses html tables so if you are comfortable changing html tables then open up the productlist.ascx page in your favorite editor and format the tables to your requirements.
To display additional product info next to the product you can enable the summary field by setting the visible property to true for the table row that contains the summary field:
<tr runat="server" visible="false">
<td>
<asp:Label runat="server" ID="lblSummary" Text='<%# DataBinder.Eval(Container.DataItem, "Summary") %>' style="float:left; text-align:left;"/>
</td>
</tr>
3. Currently there is no way for you to add customer reviews into a tab control