Is it possible to fit this Tioga Mc Groove saddle on my bicycle?
Yes, your bike can be fitted with pretty much any saddle. 

The (metric) allen key on your new saddle is a 6mm. If you're using Standard Allen wrenches its probably a little larger than 7/32". 

The seat post needs to fit your frame. So you will need to mount the new saddle on your old post, or buy a new post that exactly matches the size from your original one. 

It does sound like you've disassembled the guts of your suspension seat post, so if you can't get it back together, you're probably looking at a new seat post. 

There should be no problem mounting that seat on any post that fits your frame. 

I hope that helps.