close-ups with 70-300mm

First trial with the Tamron 70-300mm lens. As expected, the images are not very sharp, and were touched up a little in PS. All taken with the SB800 and Diffusion Dome.
Can't find one which is not damaged... (but I think the damages may have made a more interesting subject)
Dinner!!
This is just a little fellow (~3-4mm in length). Had to manually focus.
With the limitation of this lens, what can I do to get sharper images? The option of buying a proper macro lens is not quite on the table at the moment...
Can't find one which is not damaged... (but I think the damages may have made a more interesting subject)

Dinner!!

This is just a little fellow (~3-4mm in length). Had to manually focus.

With the limitation of this lens, what can I do to get sharper images? The option of buying a proper macro lens is not quite on the table at the moment...