A larger cage would certainly be appreciated by your little newt.
I would personally want to include more water in the enclosure and would probably fill it to 1 or 1.5 inches below it's capacity. This would serve two purposes: providing more volume to dilute waste products produced by your newt and also giving your newt more exercise.
I would remove the rocks/gravel and either use a thin layer of sand on the bottom or leave it bare. This will make it easier for you to clean up uneaten food and waste which at the moment will sink between the rocks and rot, quickly fouling your water.
You can easily make a sufficient land area by using floating aquatic plants like elodea or hornwort. I have had great success with the latter. You could also use a piece of corkbark, which will stain the water brown, especially in such a small enclosure.
Don't forget to include a few hides like smaller flowerpots or little resin fish pieces.
You should also regularly change the water in such a small aquarium. At least every week. A small sponge filter would also be a good investment.