Do not modify any ascx files. Doing so forks the code and that is not recommended for a variety of reasons.
You can force the child to start on a new line by using CSS:
.breadcrumbs a.breadcrumb:nth-child('2') { clear: left; display: block; }
To change the separator (>) to something else use the Separator property on the breadCrumbsControl in your layout.master:
<portal:BreadCrumbs id="Breadcrumbs" runat="server" Separator="/" />
If you don't want anything, use Separator=""
HTH,
Joe D.