I don’t think it really makes sense to sell your 2.2 kW spindle for buying a 1.5 kW spindle! As I showed above, for their rated power, your circuit breaker 15 A is too small for both of them. But if you decide to use a spindle and to limit its power inside the VFD, it does not matter whether it is a 2.2 kW or a 1.5 kW spindle. You can set both to behave as if they were 0.75 kW spindles by altering the “rated motor current” setting inside the VFD in order to stay under 16 A VFD input power.
To be clear: With a spindle with power set to a limit inside VFD, you will not notice the difference to an unlimited spindle as long as you do not put heavier loads to the spindle. Neither the speed nor the torque will be different if you limit a 2.2 kW spindle to behave like a 0.75 kW spindle, as long as you do not exceed the load (e.g. larger (wider) bits, deeper cuts, as @Dr-Al said) that you limited it to. And as said above, if you exceed the load, the VFD will just trip.
What I mean is in fact not much different than what Dr-Al said but with the difference I would not connect the higher power spindle/VFD to a weaker power source without limiting the power inside the VFD. This way you make sure that in case that you exceed the power by putting a too heavy load, it is the VFD that trips and not the circuit breaker. This is not only important for safety and for protecting the VFD, but also means that in case the VFD trips you don’t have the power out on the CNC Controller too.
So what I would say is: You have a spindle, so you could simply use it and set the “rated motor current” inside VFD to a fourth of the rated current on the spindle’s nameplate, and if your loads are like we estimated here, you will not exceed the power you can get. And the best thing is: If the load is exceeded, it is not the circuit breaker that will trip, but the VFD, which is made for that.
Also a 2.2 kW spindle has other advantages over a 1.5 kW spindle: Not only you avoid the limitation of the 65 mm spindle mount which will not allow the spindle to clear the stepper but also it has bigger bearings which means longer life. Also you need less cooling because both the mass of metal body and the mass of water inside is greater.
It is not likely that you produce fire if you exceed the circuit breaker or the VFD and it trips. These safety mechanisms are there. But what can produce fire are bad connections, both soldered and screwed. To avoid this, make sure you have a pre-made spindle cable and don’t put stranded wire into the VFD terminals without wire ferrules or ring or spade connectors (depending on terminal type on VFD) which have to be properly crimped to the stranded wires.
Regarding the test for finding out whether you have two phases and subsequently have already 240 V in your space is not difficult if you a own an extension cord of appropriate length, and a multimeter. If you have two phases and 240 V, it is clear that there is some way to have a 240 V outlet.