This is kind of a follow-up, but is the gravestone partially buried in some way? I notice that the writing on the gravestone seems to be cut off (ending at "WHO"), though I may just be missing something.

The top figure is winged death, one of the first and most enduring icons on American gravestones. For the Puritans it was a neutral symbol serving as a reminder of physical death and spiritual rebirth.

But as you've deduced the side figures are more intriguing. They appear to be a take on the paired gourds/breasts theme. Gourds were a symbol of both life and death, breasts the divine milk needed to sustain life or receive the Word of God, in effect spiritual nourishment.

This study, "Death and Dying in Puritan New England" looks at Puritan iconography in greater depth. If you happen to be able to find a stone carver's mark on the stone, that would be the best way to find out more about the imagery.