Ray, set up the form so the rows are each a group. I.e set your first three fields horizontally then pull the fourth field down until the separator spans the whole page. Then fill out that row and do the same with next field to start another new group. And so on. Then it will tab across and then down …
Its well demonstrated here by Stephen Chapman: Can I control the sequencing order for tabbing from field to field on a form? It seems to default to top to bottom for each columns of data fields - #3 by StephenChapman
That will space out the rows a little vertically (as the groups are slightly spaced out) buts its likely that CSS might be able to push them back tighter if it was an issue …