I apologize in advance if I've misunderstood what you're trying to do (or for any mistakes I make below), but the 3,600 mAH you mentioned isn't a quantity of power -- it's a measure of the total energy that can be stored in the battery. If you're charging simultaneously, your concern should be the rate of energy delivery to the battery and the rate of energy flow from the battery. Energy per time is the power, and the most convenient unit is the Watt (a Joule per second, by definition). For electronics, the wattage can be calculated as the product of current (in amps) and voltage (in volts).

You can, at most, get a few Watts from your dynamo -- let's say 5 W for convenience.

If you're powering all of your devices via USB that sets your voltage at 5 V and, accordingly, a maximum total current of 1 A.

You can set the E-Werk to a current as high as 1.5 A, but at 5 V you simply won't get that much current. The standard USB specification is 500 mA per device, but some devices want even more than that (most notably an iPad at 2 A). Perhaps some will take less, but in any event, I think charging two USB devices at the same time is an upper limit set by how much power you can get from your dynamo, independent of your battery.

I used a USB battery with a total capacity of 10 WH with my E-Werk on a coast-to-coast tour last summer. Note: since 'power in' and 'power out' were via USB, that means the voltage was always 5 V, so I can convert that capacity to the units you specified just by dividing by the 5 V: 2 AH = 2,000 mAH. And, most notably, I found that it took most of a day's riding to fully charge it, which implies that it was getting significantly less than 5 W from my dynamo.

All that said, I enjoyed using the dynamo / E-werk combination for the novelty, and I managed to complete my 56-day tour powering my phone, camera batteries and iPad via the E-Werk without needing to plug in. (Were it not for the iPad it would have been easy, but to keep the iPad charged up meant I had to constantly cognizant of using my dynamo power most efficiently. By simply plugging as available, and using the dynamo / E-Werk just as a little bonus energy, however, would have been easy.