Our help desk is designed to work with any kind of requester including external users without SharePoint account. Thus, it is not always possible to detect SharePoint user for a requester. It also is not a good practice to create items in SharePoint on behalf of other users. There is ‘Requester’ filed in a ticket for detecting a requester.
There is also ‘RequesterSPUser’ field. It stores SharePoint user id if requester has SharePoint account. It is hidden by default and can’t be used in SharePoint user interface to create new views. It is available only if you create views programmatically.
Our default design assumes that if you want to restrict permissions on tickets, then you should place a widget to some other SharePoint site. The widget is an entry point for requesters. Agents work in help desk itself.
Restricting permissions on list item level permissions can lead to performance degradation of SharePoint. It is always better to restrict permissions on a higher level. You can find more details in this article. This is one more reason why we didn’t use item level permissions.
Anyway if you want to assign item level permissions on tickets, you can still do it with the help of SharePoint Workflows. You can start a workflow on ticket creation and use another our product called Workflow Actions Pack to assign item level permissions.
Regarding the error with placing widget on a page. Could you describe steps to reproduce the issue and share a screenshot of the error?