Issues with simulating TL494 in PSpice

I apologize if this is a duplicate, but I have looked around and what were solutions for other people's problems did not work for me.
As a part of a project, I am trying to make a 48Vdc supply that plugs into 220Vac. Instead of using a transformer I would like to design a buck converter. Here's what I came up with:

I simplified the schematic so that it does not include the rectifier, just the buck converter. Also, I separated out some parts of the circuit into subcircuits because I think it is easier to understand what's happening that way. Here are their schematics:

For the controller I chose TL494 for various reasons, the biggest one being the fact that this is new to me, and the datasheet for TL494 had a very nice Example Application section. I need to be able to simulate it because I don't really know how to select a frequency otherwise. After attempting to simulate it and getting a convergence error I turned on auto convergence and got it to simulate (graph.png) for about 100us, but any more than that gives me a overflow error. The frequency seems to be stuck at 40kHz unaffected by the values of Rt and Ct.

Here is the convergence error:


Both errors seems to happen around the time the first pulse should be happening (see graph.png). Another thing that confuses me is the 256A at V1.
I guess this is the only info it gives me for the overflow error:


Other than solving the error and understanding why I cannot change the frequency, I would like to know why there is a pulse on Vg at the very start.
If there is anything else I should post please let me know. (I can simulate the 100us and graph more things if needed)