AFAIK, currently the max bet is 1BTC. Previous to that it's been .1BTC, 1BTC and .1BTC.
With respect to scripting/bots; set your min and max variables in code, don't rely on the MP API. I've also learnt the harder way.
Yeah, the max bet has been 1 BTC for quite a while now. Due to the problems and confusion when I increased it, the normal strategy has a: "Stop if bet is > ____ bits"
and the custom strategy has:
console.log('The max current bet is: ', engine.getMaxBet()/100, ' Bits');
which prints:
The max current bet is: 1000000 Bits