What's the general efficiency of a 12v 100Ah tubular battery?

[MrOmnos]

I have a UPS/Inverter system which consists of a 100Ah battery and a 800VA UPS. In an event of power outage these are the items that are running at any given time:
1x9 watt CFL

2x laptops (power brick says 90 Watts for one and 50 watts for other, we do not have laptop batteries inserted. I am not sure if the power consumption is same without laptop battery charging)

1x raisecome passive optical network unit (datasheet says power consumption of <=10 watts at max  load)

1x Netis Router WF2419 (provided by ISP, power consumption unknown, requires 9v 500mA power brick. I am assuming 5 watts)

So, Total Power consumption is = 9+90+50+10+5
                                                   =164 ~ 165 watts
                                                  = 165/0.8 = 206.25 VA

Assuming battery efficiency is 90%, batter capacity = 90Ah

Therefore, amps = 206.25/12 = 17.2

               Total  Backup time = 90/17.2 = 5.23 Hours

Now the questions

First of all, is this calculation correct?

I assumed 90% efficiency for the battery, is that the efficiency of a tubular battery found in the market?

What is the power consumption of the a normal laptop without the battery charging?
I don't have a power meter, should I use a MM to measure the current drawn by the laptops to know the power consumption?

I am going through all this to check if my battery is working properly and just to learn about things. Thanks