If you have switches with 2 lit lamps at all times (one on switch, one on controller) that can be quite a burden - almost 2 Watts per switch. So with 19 switches, that's over 30 Watts which is quite a tax on a 180 Watt supply.
I have never seen a comprehensive study of power requirements for engines and accessories for O-gauge. A DCS engine at idle may draw up to, say, 5 Watts. Pulling nothing and meandering along at 10 sMPH on straight section an engine might draw 15 Watts. Pull a few cars around a tight curve and you're at 30 Watts. Add a few more cars and climb a grade and you're at 50 Watts. Turn on smoke and add another 5 Watts. A lighted passenger car - another 5 Watts per car (unless converted to LED).
Accessories can add up. There was a recent thread about some new Menards lighted buildings using LEDs (a lot of them); even with LED technology the building requires over 10 Watts! That same building using incandescent bulbs would need, say, 50 Watts to provide the same brightness. Yikes!
Your DCS/TIU box requires less than 5 Watts. But with 19 switches, I see a DCS/AIU in your future. 
The AIU switch controller is powered by the TIU. So add a few more Watts.
As the guys above suggest, get another transformer, wall-wart, whatever to power anything that is not rolling.
Most accessories operate on DC or AC voltage. The DCS/TIU can be externally powered by DC or AC. To the extent you can use DC, you will find DC power costs about 10 cents per Watt whilst AC power costs 5-10 times that.
