The Army found a condition with my son's heart after being bit by a spider, how long will the process of being chaptered out take?

The IDES process was recently updated to take no longer than 180 days. But there are other variables. Depending on the condition, he may be perfectly capable of managing it with diet, exercise, and medication. If he is referred to MEB, once that actual referral happens, he won't usually be chaptered, he would usually receive a medical separation. Unless its determined that it was a preexisting condition, then he doesn't get anything, unfortunately. It could also result in a medical retirement, but at his age, time in service, and capability, the Army probably isn't going to find him disabled enough to retire.

That depends on a number of factors.
If he is in basic training or Advanced Individual Training (AIT), it could be measured in weeks.
If he has completed training and reported to his unit it may be measured in months.

Every situation is different. This is best discussed with your son’s physician and his chain of command. The physician and command team will work together to make sure his health isn’t put at risk while his medical board process occurs.