When a defendant posts bond, that is his promise to appear at subsequent court dates. If he bonds out, he must appear.
A defendant can bond out at any time if the defendant can post the required amount of money to assure his appearance. A bondsman will put up the 75,000 for you if you pay typically 10% up front for the bondsman to keep. It then becomes the bondsman's job to help the defendant appear for court.
Yes he could bond out before pre-trial. Yes, he would need to appear unless the court reschedules him. The court would only re-arrest him if he failed to appear, if the bond amount were raised due to some decision of the court that the amount is insufficient to guarantee his appearance, or if the court had other charges that the defendant hasn't answered for.
Yes he will be eligible to bond out if there is no other pending case or charge against him.
All of these answers change if there are other charges or circumstances that inspire the court to change the bond amount.
If there is a bond set for your friend, he (or a good friend or family member) could post that bond at any time and he would be released. Usually bonding companies require about 10% of the bond to be paid as their "fee" and it is non-refundable. Additionally, the bonding company would likely require collateral (cash, deed to a house, etc) for the rest of the bond. The bond is a guarantee that the defendant will appear at court--on time, everytime. He will not be arrested again for this offense as long as he continues to appear at all court dates as required. If he picks up a new case while on bond, he will likely be arrested for that and violating his conditions of bond.
Once someone bonds out of jail, they are required to appear at all of the court dates, including the pre-trial. If he fails to appear, the court will likely revoke his bond and issue a new warrant for his arrest. At that point, it may not be possible to get another bond. If he skips out on his bond and does not appear, the person who posts the bond will be responsible to pay the balance owed on the bond ($75,000-10% paid) back to the bonding company.
I hope this answers all of your questions. Good luck to you and your friend.
If your friend bonds out, then he would have to appear at his pre-trial hearing unless the court gave him a different date. He will not be arrested again if he is already on bond - the purpose of the bond is to ensure that he appears in court when he is scheduled.
Even if he does not bond before his initial appearance, he can bond out at any time during the course of the case.
Assuming that he has a hired lawyer, if he bonds out, most courts will require him to hire his own lawyer so be prepared for that. (It may not be right if he is eligible and someone else makes his bond but most courts treat bonds in that manner.)