When you select Set Tab order from the layouts menu, what do you see for a tab order?
Do you have any script triggers specified for the portal or the fields in the portal?
And I do not understand your second question. :(
If this is a database of your own design then you won't have script triggers as you don't appear to know what they are. Script triggers are something you can look up in help to learn more, they're a way to perform a script when the user interacts with a layout in a specific way such as entering field, exiting it or pressing a specific key. Since the script could put the cursor in a different field than specified in the tab order, this could interfere with the expected behavior.
What you have looks like it should work.
When I press tab in my portals, tabbing out of the last field in the row moves me down to the first field of the next portal row, so I'm unsure why this is not working for you. You might try creating a new copy of this layout from scratch to see if you get the same behavior in the new layout.