Transformers, input voltage range

I would not recommend that: it would result in enormous power wastage. The reason being, during the on part of the PWM, the circuitry (and cables, component leads etc) between the mains supply and the capacitor would be acting basically as a (very low value) resistor which would dissipate the heat. For example, the approximate average voltage across the MOSFET/cables/rectifier would be 200v. In other words, very inefficient. Lastly, There would have to be a current-limiting feature controlling the MOSFET, otherwise the surge in current would also blow fuses, because in essence it would just be one giant short circuit.

But yes, regarding the peak current through the MOSFET, the MOSFET will have graphs and other specs which will define separately, the peak current (for example over extremely short pulses) as well as a total power dissipation which if the MOSFET is pulsed on and off could essentially be doubled for your purposes. But calculations would have to take into account the effectiveness of what heatsink you have etc.

Useful to have added was the transformer's catalog page which is where the DC spec came from.

With various similar versions here

Best view of the selection table is here where you see all models and all parametrs in a single page.

These transformers are designed to be "flyback" power supply operation and are designed for differing and specific operating frequencies - see table.

The smaller core sizes give a wide range of versions with differing DC ratings. These appear to be the DC input voltage which will drive them to about their peak current rating during a typical flyback cycle at the specified frequencies.

If you apply a higher voltage than stated the peak current will probably be reached in a smaller time than is expected at the rated frequency and so switching will occur sooner and resultant frequency will be higher than specified. This MAY be acceptable and may not, depending on what factors were optimised in the design for the target frequency.

Without knowing your exact requirement a best choice cannot be recommended, but this series seem better suited to your need, with mains rated inputs and some with approxiamtely the same power ratings as you indicate. That said, the one you have chosen initially may indeed work OK.

Probably not applicable here but, as well as primary to secondary isolation, the layer to layer insulation in a transformer can matter. eg if a winding has N layers then the voltage change per layer is Vin/N and if layers are woune alternatively left to right then tight to left you get a voltage difference of 2 x Vin/N at each end or a winding. This can matter in higher voltage applications.