They didn't really worship the cat. They had some cat like gods that dominated public attention at different points in history and considered them v.i.p.s essentially. They were more superstitious and thought cats had some kind of uncanny intelligence by virtue of being sons and daughters of Bast and that she would not be happy if she heard about any disrespect.

There were specific temple cats that sometimes b breed too fast and had to have litters sacrificed and mummified and repurposed as holy symbols, and foreigners could be beaten or killed for being cruel to them

I think its time for a bit of clarification on this question, its a popular 'factoid' about Ancient Egypt and as such has been victim to quite a lot of over-simplification. Namely (albeit pedantically), Ancient Egyptians did not worship cats. We can blame Herodotus and Diodorus Siculus for that little snippet

However, before we get to that lets deal with your first question. Estimates of any population are always limited by the available data. For instance estimates of the population of people in Ancient Egypt in any period are based principally upon agricultural capacity with factors such as settlement distribution, estimated economic prosperity, effects of natural catastrophes, limitations of warfare, estimates of immigration etc acting as factors to tilt the figure up or down. In general Ancient population estimates are a hugely contested area of archaeology. The Ancient Egyptians were master bureaucrats but we have nothing like a census to refer back to, the best sort of evidence is from well preserved villages such as Deir el-Medina or Kahun. In these cases we have the number of houses, fragments of work attendance lists, letters etc allowing us to reconstruct a limited prosopography for the settlement. So we have a limited capacity for estimating the population of Ancient Egypt, animals are a different matter. Completely wild animals I'm sure statisticians can work some mathematical wizardry and extrapolate backwards from more modern records and reconstructions of the Egyptian climate but domesticated animals require a completely different set of questions. The cat population of any settlement will be principally governed by Egypto-feline relations...which brings us to your second question and why I reject the idea of 'cat worship'.

Cats were not worshipped, gods were worshipped and gods were sometimes presented zoomorphically as cats. Try not to perceive Egyptian gods in the western-hollywood-esque/fantastical/fictional tradition of magic beings. The best way to imagine them is as natural features with a conscious. These entities were typified by a diverse array of characteristics: life, fertility, dancing, music, death, protection, might, intelligence, justice etc. Egyptians saw these characteristics in animals, people and in rare cases in the topography (e.g. Hapy's blue skin matching the Nile or Aten's rays of sunlight).

So famously, the majority of representations of Bastet are as a cat. Egyptians equated some of Bastet's features (fertility, music, protection) as embodied by cats. But Bastet was not the only deity depicted as a cat. Re was also represented as a cat, for instance this scene from the Book of the Dead where Re, as a cat with a knife of all things, defeats Apophis, depicted as a snake. In a less aggressive scene from a stela concerning peacefulness and forgiveness the cats represent Atum (right) and Re (left). Representations of such deities are fluid within Ancient Egyptian art and as such it is sometimes difficult to pinpoint which deity is being represented. The Gayer-Anderson cat for instance has no markings or labellings which suggest it is Bastet, arguably it could even just be a statue of a particularly loved moggy, Bastet is presumed from its dating to the Late Period and not its provenance or style. We also have ostraca showing people with their hands raised in front of the 'great cat of Mut' (O DeM 3136) and a bizarre juxtaposition with Hathor on a stela of Bukhanef from the Ramesside period.

Some depictions of cats represented characteristics of gods but not all. Occasionally depictions of cats were not complicated by religious symbolism, they didn't represent anything but a pet - Ipuy (TT217) has no fewer than 3 cats in his tomb paintings and as much as I dislike reading realism into Egyptian art, for anyone who has owned a cat its pretty hard not to understand the gesture this kitten is making. We even have cats in illustrations of stories, like a comic, O DeM 2305 has been quite widely discussed as it seems to depict a chariot battle between cats and mice or O DeM 2202 concerning a conversation between a cat and a duck.

This medley of associations didn't always work out well for Egyptian cats though. When the sacred animal necropoleis gained popularity in the late period and the animal mummy industry became more prevalent, cats were bred purely for mummification purposes, like ibises. Earlier still P. Ebers' recommendation for getting rid of mice is to wipe the fat from a cat around the house.

All in all this seems a thoroughly unhelpful answer to your question, no idea as to population and no they were not worshipped.

P.S. Don't worry about kittens, most mummified cats were adults.

Bibliography:

• Malek, J. 1997. The Cat in Egypt.
• Sweeney, D. 2009. 'Cats and Their People at Deir el-Medina' in Sitting Beside Lepsius, Magee D et al (eds).
• Neal, J. 2012. 'The Life and Death of the Sacred Cats of Bastet' in KMT 21
• Ikram, S. 2005. Divine Creatures: animal mummies in Ancient Egypt.

EDIT - had to stop due to boss nosing around when I should be working.