This can easily be done.

Please follow following.

1+2. Add following code in Front End PM PRO > Settings > Appearance > Custom CSS . This will hide both welcome section and menu.

#fep-header, #fep-menu {
	display: none;
}

3. Go to Front End PM PRO > Settings > Recipient > Max recipients and set to 0 (zero). This will hide “To” section.
4. Go to Front End PM PRO > Settings > Recipient > Can send to group and checked. This will enable group message option.

Let me know if you find any difficulty.