After reading through a bit there's always going to be conflicting views on the "perfect settings" or the best type of shot ect ect.
One of the most important things when taking photographs of reptiles is take into account the background this is essential.
You can have one of the rarest or most beautiful snakes out there but if you put it on a manicured grass lawn or around plastic plants or worse exotic plants ( if the snake is indigenous) it just detracts from the image.
I see many people suggest a shallow depth of field( as you used in the latest series of photo's) which are nice with a few adjustments you can make them great photo's.
You have a good DSLR camera so USE it!
I recommend you learn to shoot in M or manual shooting in anything else in regard to snake or reptile photography is simply limiting yourself and DONT USE Autofocus as you may as well just use a point and shoot.
I used the standard kit Lens 18-55mm with great results it's a great little lens.
The lens is the sharpest at around F16.
Next time you're out try out these basic settings
F16
ISO 200
Shutter Speed 1/200
Remember when you're shooting in M always use the flash and shoot in area's of full light as that will get you far, lighting is everything!
But the most important thing is have fun whilst you do it!