Try the IR2153D for your circuit. This is a self oscillating power FET driver designed expressly to properly drive the FETs. A side caution: Those metal cased resistors like that are rated at their full power rating when clamped to a heatsink that limits the maximum temperature. They can EXPLODE VIOLENTLY if they are heated hot enough!
The reason you're seeing different voltages between your oscilloscope and your multimeter is that the oscilloscope is showing the peak-to-peak voltage where most multimeters show AC voltages as either estimated RMS voltage or true RMS voltage, depending on how good of a multimeter you have. By using the RMS version of a voltage measurement instead of peak-to-peak, it works better for different waveforms (square wave vs. triangle wave vs. sine wave, for example) and it fits nicely into the same resistance calculations (Ohm's law) that DC does. In other words, if you use the peak-to-peak value like what your oscilloscope shows, you would have to do different and more complicated calculations to properly design circuits. RMS simplifies things a lot, and is a more accurate representation of how much power is actually being pushed down the wires. I hope that makes sense.
I haven't done a full analysis of your circuits to try to explain them, but a few things I'm noticing: 1. Early in the video, you're wondering about the different voltages. Keep in mind that diodes have an inherent voltage drop - usually around 0.6V - so you're going to be losing some voltage there. 2. The diagram on the transformer at 12:54 shows the center tap with a positive voltage. I'm wondering if your transformer's center tap is not actually at the center. They don't have to be. Some multivoltage transformers can have center taps biased toward one side or the other so you get a lower AC voltage which you can then rectify if you need DC. But if that's the case, the 7.5V line should still be AC since it's referenced to the rectified ground. If the capacitor on that line is polarized like an electrolytic, you could destroy the capacitor. If it is nonpolarized, then it should just shift the phase of the AC's voltage/current. 3. The reason the big resistor is getting hot at 12:32 is because you're effectively shunting the full power of that voltage rail through both it and the MOSFET. You're basically using it as a heater. 4. Have you heard of a 555 timer? It would probably help you a lot with what you're trying to do. Lets you make very simple circuits. 5. I love the little labels you put on things. It would make it so much easier to understand peoples' circuits if they did that. Hard to read color codes and etched-on numbers on parts from a video otherwise.
