The math
If you're looking at this from a simple exponential growth equation perspective, as your mention of 1.0012 implies, then these would all be factors feeding into what a plausible growth rate would be.
Note that if the exponential growth equation is written as
F = P * (1+r)^t
F= Final population (or value)
P= initial population (or principal)
r= rate
t = time in years
then you really need to write the rate as, e.g., 0.0012 rather than 1.0012. This allows you to do a trick / rule of thumb called the "rule of 70".
For that, you turn the rate into a percentage (0.0012 = 0.12%) and divide 70 by that number. This will give the "doubling time", the time needed for the population to double,
to a reasonable approximation. (This is more commonly a financial thing, sometimes with 72 instead of 70 - it's an approximation, not exact - but the math of exponential growth is the same.)
So a growth rate of .01 is 1%, 70/1 = 70, so population doubles every 70 years.
.0012 is 0.12%, 70/0.12 = 583. Population doubles every 580 years or so (this is a rough approximation). This is a really slow growth rate.
Doubling time may help when you think in terms of generation times.
If you change time to adulthood, generation time, and lifespan but keep everything else proportionally the same, the annual rate will ll change.
A human population might have a generation time of perhaps 25 or 30 years, so if the population doubles every generation, then that's also the doubling time - meaning a population growth rate of about 2.5% (70 / 2.5 = 28). This is pretty extreme.
But let's say this species only lives to 20, but reaches adulthood at 4 or 5, and generation time is 7 years. There's still a doubling every generation, but the annual growth rate is now 10%! (70 / 10 = 7).
Conversely, if that species lives to 500, reaches adulthood at 100, and has a generation time of 140 years, doubling every generation is now only an 0.5% annual rate (70 / 0.5 = 140).
Practicalities outside math
However, population growth isn't that simple. There isn't one number for "ancient/medieval" human growth, even in a single area with a long recorded history such as China or parts of the Roman Empire; over that long time span populations changed dramatically, with declines due to plagues, famines, infrastructure collapse/invasion, etc.
In most real world cases, it's not the actual reproductive capacity that sets a limit to population growth rates. An oak tree can drop a huge number of acorns, but there's no room for all of them to grow into full-sized trees. And for people/intelligent beings, you need to consider social/cultural factors too - e.g. many current wealthy nations have below replacement birthrates.
But in a hypothetical situation without those sorts of constraints (an example would be settling a new area rich in resources and without competitors) ...
Your specific points
have less females than a 50-50 split, perhaps only one third of population is female, perhaps only one tenth
For mammals, reproductive capacity is basically determined by the female side of the population, so this will be a dramatic decrease.
only need one individual to reproduce
Basically the opposite.
gestate for longer or shorter amounts of time, a year or more, a month?
have more offspring per reproductive cycle, instead of one maybe 2, or 3, or 7
The key here is the number of offspring possible in a reproductive lifetime. If the normal birth is triplets rather than single, but the number of births per mother is the same as ours, that triples reproductive capacity. If there's also twice as many births in the same reproductive lifetime, then it's 6x.
(Gestation time isn't the only factor here; if the species has an annual reproductive cycle timed to e.g. availability of food in spring, there will be no more than one birth per year per mother, even if gestation time is very short.)
live for shorter or longer amounts of time, maximum age of 20 rather than 70-80, maximum age of 500 rather than 70-80
Lifespan/generation time effects were covered above.
(One small note here is that in humans, due to menopause, reproductive lifetime ends long before overall life span.)
