>>>> Question1: When AC is run by Honda generator, how much more power can be consumed?
I believe you have a 13.5k BTU Air Conditioner in your 2016 23D unit (vs the larger 15k unit in the 25').... you will have a little power left over, but just for smaller stuff. On a hot day your Dometic Penguin 13.5k BTU Air Conditioner will pull up to around 1600-1700watts steady state running. Your Honda 2000 is a beast, but is rated for 1600w continuous, 2000w max (technically for 30 minutes), and that is at sea level, running with gasoline.
Do you have a little bit of additional overhead to charge a laptop, but not enough to run your fridge on AC for example. 2 machines at 250w each will likely not run. Maybe one but likely not two.
>>>> Question 2: While running AC, how much power is being sent to the charger/converter to charge the batteries?
A small amount, perhaps 10-20 12v
DC amps to the batteries if the Honda is at full throttle. The converter will first supply 12v
power to items in your trailer like lights, fans, before any residual current is drawn into the batteries for charging.
>>>> Question3: When generator is providing power, can the onboard inverter be used safely?
Yes absolutely. These are independent systems in your trailer. The inverter outlets are powered exclusively by the battery via the inverter, your other outlets are directly wired to shore power. If you have 2 stock lead acid batteries, fully charged, you could run your two 250w desktops for about 2.5 hours before your batteries hit the 50% discharge level, at which point you will need to charge them back up.
Run your AC when you need it. Use your inverter for additional 120v power if needed for charging stuff. If you have all this gear you can also just load it all up and experiment to see when the Honda goes into overload protection (you won't hurt it).
When you turn your AC off, just leave the generator running and the converter will use available power to re-charge the batteries. Just don't let them get below 12.2v and you are fine.
Finally, note that elevation will reduce generator output. You will loose about 3% of power output per each 1,000 feet above sea level. for example, I live at 5,000' and camp often at 8-9,000 feet. That's a ~25% power loss on gas at 8-9,000 feet. Too much loss to run the AirCon on Honda 2000 alone at that altitude. if you are considering a propane conversion for longer runtime using your onboard propane tanks, note that propane also lowers output as well. Loss is an additional about 5-10% in my experience. Just FYI.
If you are 100% reliant on running both AC and your desktops, you will likely need to consider upgrading to a Honda 3000, that would be your least expensive path vs. a large lithium battery bank.