I'm having difficulty recreating the scenario in our environment. Do you mind sending us a sample project so we could recreate the scenario and replicate the issue easily?

In order to use the modified wglang_it-IT.xml you will need to use CommonLibrary virtual directory. Here is the snippet:

<TextSettings Language="UseCulture" 
    LocalizationFolder="/CommonLibrary/WebGrid/V7_0_7200/Localization/" 
    UseLanguage="it-IT" UseWebResources="False">
</TextSettings>

Have you tried using CommonLibrary in the Sharepoint environment instead of using SmartWebResources? perhaps it could solve the CPU issue as well.

You could read in more detail regarding deoplying without smartwebresources on our WebGrid documentation in the article Deploying project that does not use SmartWebResources

You will need to use similar method with the Grid View.  You will need to use cell template in order to bind complex object property. Here is the snippet:

<ISWebGrid:WebGridColumn Caption="Sun ETID" Name="SunETID" ColumnType="Template">
<CellTemplate>
    <asp:Label ID="Label1" runat="server" Text='<%# Eval("Sunday.ETID") %>'></asp:Label>
</CellTemplate>
</ISWebGrid:WebGridColumn>

I have confrmed this issue with our developer, our WebCoverFlow will be loading image from the client side.

As demonstrated in this thread, our WebCoverFlow has the ability to load image from an external source.

WebCombo already support binding with multiple data source. Your scenario would be similar to BindDataSource.aspx sample. In my test, using WebService to return List object and DataTable object, I did not encounter any issue.