I took 12.5mg of ALA then lowered it to 10mg the day after. It's not advisable to mess around with the dosages though. Choose a dose then stick to it. I also took DMSA two days before taking ALA but it didn't agree with me (though I did carry on with it).
The feeling good phase came on about 5-7 days after finishing the round. It was due to a combination of things, eg supplements, being in the sun, drinking tons of water, not just the chelation round.