Hello,
Fresdorf does your cheap ring flash get a HSS mode ?
If it don't, you can only use it at sync flash speed of your camera.
The sync flash speed of pentax camera it's 1/180.
So a ring flash that doesn't get a HSS mode, with a pentax camera you can only work at 1/180 or slower speed.
Your D3100 get a sync flash speed of 1/200.
So without HSS mode you can only work with 1/200 or slower speed.
Did you try to work with manual mode.
In this way you must choose the power of the lightning.
It can be, not easier for you, but better for the quality of your lightning.
For a better gear you can use some of them :
takumar 50 f/1.4
SMC 50 f/1.7 - f/1.8
pentacon 135 f/2.8
superTAK 135 f/2.8
superTAK 105 f/2.8
helios 44M 58 f/2
etc... etc... etc...
with macro extension tubes.
Or as reversed lens, you have already use this way to work, i see some of your photo taken in this way.
Or again an old M42 macro lens with a TC or extension tube to get the 1:1 ratio.
M42 lenses can be cheap and get very good IQ if you close beyond f/4 or f/5.6.
Some of them are not cheap at all but the cheap lenses are very good.
Take a look at the flickr stream of john hallmen.
He get terrible photos with old lenses, his photo stacks are astonishing.
johnhallmen's photosets on Flickr My (old) Macro Rig | Flickr - Photo Sharing! 9 lenses at 2.5X | Flickr - Photo Sharing! Setup... | Flickr - Photo Sharing! Modular Macro Diffuser | Flickr - Photo Sharing!
Don't worry, my first proxi/macro photos were not terrible at all.
They were ugly, your shoots posted here ar really better than my first shoots.
I delete all of them and only keep the photos really good.
You need a lot of practise as we did to get better photos.
Here with 18-55mm kit and raynox mounted on a K-x
http://octopussy.fr.free.fr/insecterra/_IGP0087.jpg http://octopussy.fr.free.fr/insecterra/_IGP0090.jpg http://octopussy.fr.free.fr/insecterra/_IGP0092.jpg http://octopussy.fr.free.fr/insecterra/_IGP0097.jpg
Here with sigma 105 mm macro and dcr-250 or MSN-202
http://octopussy.fr.free.fr/pentaxforum/_IGP5725.jpg http://octopussy.fr.free.fr/pentaxforum/_IGP5709.jpg http://octopussy.fr.free.fr/pentaxforum/_IGP5675.jpg http://octopussy.fr.free.fr/pentaxforum/_IGP5689.jpg (just the 105)
Here with sigma 105 macro + tc (1.5x) + raynox
http://octopussy.fr.free.fr/pentaxone/_IGP2638-800.jpg