Can I possibly continue? Is it wise to enable all labors for the mayor and have him run the whole fort?
Yes, quite easily, provided he isn't already insane with grief. If he's pretty sad arleady, you may want to get him burying bodies asap. Otherwise, keep him safe inside and leave the body-burying for later when migrants arrive. Give him the biggest damn bedroom, dining room, and office if he doesn't have them already. Once that's done, you want to dispose of or stockpile anything inside the fortress that might rot, fortify the defenses with more traps (as migrants won't do you any good if an ambush is sitting outside your locked gates). Seal off any breached caverns as you can't deal with a forgotten beast, and ensure you've got plenty of booze or a water source for when migrants arrive. Not necessarily in that order, either.