Burning Oil + Coolant = Overheating

[2009ToyYaris]

Help!!

-Vehicle History-

2009 Toyota Yaris, 235K miles. It has never seen a professional mechanic, I have done all the maintenance myself.

-Coolant-

My one neglect was never checking the coolant until recently ~8k miles ago.
When I did check the level through the hose cap it was near bone dry. So I flushed it and filled it up with the red Toyota coolant. I took about a gallon out, but the car only let me put back in about 3/4 gallon, until the next day I was about to put the rest of the gallon.

-Oil-

Started using regular 5w30 Conventaional oil.
-I have been using Valvoline 5w30 Conventional High Mileage after 100k miles.
-Switched to Valvoline 5w30 Full Synthetic High Mileage at about 215k.
I change the oil and filter every time the maintenance indicator comes on, about 5K. The last three time it has been about a quart low. This last change I switched to Mobil 1 Full Synthetic High Mileage, Because I couldn't find Valvoline in-stock.

-The Overheating Problems-

I was driving to work in the morning about 65 degrees out.
My engine usually is warm by time I hit the freeway. This particular day the engine cold indicator came back on. It was followed but a hot indicator, back to cold, back to hot. I immediately pulled off the freeway and opened the hood to let it cool down. This drive was a total of 4.6 miles

After 20 minutes of cooling down I checked the two fluids. Coolant was empty and the oil was not showing up on the dipstick. Poor engine, I gave it a little bit more than 1/2 a gallon of distilled water(the only amount I had in my car at the time) I'm sure it could have taken more water and a $13 dollar quart of 10w30 full synthetic oil, because they didn't have 5w30 at the gas station.

Drove it home and I had to take a chevy to work how embarrassing lol

Any reasons why It depleted my two fluids, I don't have any leaks under my Yaris. I was thinking of a possible blown head gasket knowing the warm engine turned cold then hot(possibly fluids mixing and sudden temperature change.)
Also the day before I took it to the store (5 miles away) the A/C was not blowing cold, nor was the heater blowing hot. The fan was just putting out room temp. Before this I would drive to work and a total of 25 miles each way with speed upwards of 80miles and the Yaris' engine would perform fine.

Thanks for your time.