Dell U2410 Calibration issues

Hi, last week I purchased a Dell U2410 A10 monitor for retouching purposes. At the same time I also bought the Spyder 4 Pro. I am now up to my 15th attempt at calibrating the screen and for some reason it simply will not reach the settings I need! I am hoping someone may be able to offer some help - I have searched numerous sites to find a solution but it seems my problem may be unique.

The factory calibrated settings i.e. Standard Mode with supplied ICC are way off the recommended settings of 6500k temp and 2.2 Gamma. So I decided to calibrate the custom mode to give me more control over the RGB values.

Here are the results I've had so far:

Custom calibrated:

Brightness/Contrast: Lots of combinations tried, I'm able to get to the desired luminance with very low settings of B7 C45

R85 G85 B76 which gives a colour temperature of 6500k

1.6/1.7 maximum Gamma after playing around with the settings as much as I can

SRGB calibrated:

B7 C45

7100k

2.1 Gamma

SRGB with supplied ICC:

B7 C45

7100k

2.1 Gamma

When I went through the Spyder calibration there was an option to test the colour temperature on different settings. I tried the calibrated SRGB (which gave a gamma of 2.1) with Custom mode and it gave me the desired 2.1 (closest I can get to 2.2) but if left on Custom mode and tested, it then reads the Gamma as 1.7 again.

I know that I am doing something wrong here, I just can't figure out what it is! No matter how many times I calibrate the screen, every profile gives the same Gamma reading of 1.6 or 1.7. I've played around with all settings on Custom mode including the RGB channels and adjusting brightness and contrast but it makes no difference. Is it normal to have to set the brightness and contrast that low to get to a luminance of 120? TFTCentral list their settings as B30C50 but this was an older version. Why is the Spyder4 not calibrating the screen to 2.2? (Even tried setting it at a target of 2.8 and it still gave the same results). 

I'll admit this is my first time calibrating a screen so I apoligise if I have missed something obvious! Any help or advice will be greatly appreciated.