What you are looking at is 70amp main breaker which means you can only have a total of 70 amp draw on those breaker. The one outlet on that wall is probably connected to other outlets or lights as well. I was talking to a inspector a week ago and he was saying on a 15 amp breaker you have to limit the draw to less than 2000 watts other wise you can have troubles. especially with older wiring, he also said that under the electrical code they go by the number of potential outlets and lights on a circuit and not the draw on the circuit.
I think he is right to use the draw on the circuit it does make since. As for do you have room well if you take the outlet that is on that wall out and remove the line and run 2 new dedicated lines to the panel you should be OK. I would look at upgrading the panel to a 100 amp at the least in the near future if possible I would go to a 200 amp service which would mean a new panel and a rewiring of the panel. Also I found out if you don't have a GFI on the tank circuits your insurance will be void if a fire is caused by a short in that circuit. You have to by electrical code have a GFI on outlets that are withing 1.5 meter of water. They will have to pull a permit to do the job and ask how much it would cost to upgrade to atleast a 100 AMP service. My mom is doing it and she has to move her mast and panel. 3000.00 you get it all back in value to the house.

Bill

I hope this helps, I would have a electrician take a look at it if you are not sure. They can do the calculations for you and give you a estimate on doing the work and then your house is covered.
Bill