My nails look thick and split will nail putty help ?

Yes, nail putty will put the moisture back into your nail plate.

I think I have a fungal nail infection, will nail putty cure this ?

Fungal infections can be difficult to treat and you would need to see a podiatrist to effectively diagnose your problem first. Nail putty helps in prevention of fungal infections ,but, it is not designed to treat them.

I have been using the shellac nail polish on my nails and it has ruined them will Nail putty do any good ?

Nail putty is great for dry damaged nails from shellac and will need to be used as an essential part of nail recovery.

Can I just use a cream on my nails ?

No cream sits on the surface of the nail and does not sink in like Almond oil and shea butter.

My nails have a white chalky appearance how do I treat this ?

You need to gently file across the surface with an emery board and remove the dead layer of nail. Then apply nail putty to the nail beneath to restore the moisture.