When it comes to bio agents, I'd think something like the pneumonic plague or a fungal agent would be better. More natural carriers than ebola or any other viral agent. Small pox could work, easily enough to modify it to break vaccines as some aussie shit heads did with mousepox and its own vaccine back in like 98 IIRC. Also very infectious, has flight characteristics of smoke particles.
VX, while horrifying, requires multiple dosing to a large area to get desired effects. Chemical agents may be very effective area denial tools, but the lingering costs are minimal compared to that of a severely infectious biological agent.
Ebola is simple enough to avoid once it is a known problem in an area. Since it can't spread through the air, primarily through bodily fluids, it makes it significantly less infectious but dangerous none the less.
If there was a very heavy animal presence, then any bacterial or fungal agent could be introduced very easily. Any rodent infestation can become a breeding ground for the Plague like the good old days in China. And unlike modifying a viral genome that requires a Bio-Chem major (there are volumes of reference material for introducing new genes into different types of viruses), you can heat up any bacterial agent with careful and monitored dosing of anti-biotics of various types.
With the various gear you provided, it wouldn't be too hard to get enough biological material into the city with the howitzers/supersonic drones/rocket arty you could cause some serious chaos. Add in a generous helping of the CF3 to set hardened structures on fucking fire, and you got a destroyed city with no reason to not nuke it to kingdom come. Though a neutron charge would be a better idea to sterilize the contamination with limited fallout of biological agents.
And yes, you have enough robots to do all of this remotely.
Read Demon in the Freezer, find out how the Soviet Union helped save the world from smallpox (while developing their own Germ warfare) by supplying probably the most /k/ doctors to ever exist with as much nearly expired smallpox vaccine as they could.
Please keep in mind that this is all hypothetical talk about a fictional city. Not a how to manual or endorsement to do any of this shit.