Hi,.
I recommend to read through I2C specification.
We professionals do this, too.
No need to read through all, but at least the index and some sections you find useful for your design.
There is a section that describes the hardware including pull up.
Just some raw information:
It depends on a lot of things. Bus length, bus capacitance, bus voltage, devices on bus, SCL clock frequency, driving capabilities on the bus...
So for short busses a single pullup on each line with value of 10k down to 1k should work. With 1k you should be on the safe side.
Using 4k7 || 1k || 1k causes a lot of current (depends on VCC which is unknown).
If your master can drive this current
* without being overloaded and
* while maintaining valid LOW levels
everything is O.K.
So for high speed and long busses you need low resistance.
For low speed, short busses, long battery life, good LOW levels one will consider high resistance.
Klaus