I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. I regret that my state board of veterinary examiners doesn't allow me to speak to customers by phone in this venue but other experts in this category may be able to assist you in this regard. Please let me know if you'd like another expert to do so and I'll opt out of this conversation. Please stay in the conversation if you wish.
1. Dead birds need to be refrigerated prior to necropsy rather than frozen. It's always worth knowing why you're losing birds and most important when you have a sizeable flock. Necropsy may be the only manner in which I can know what's going on. When dealing with chicken coryza depopulation to remove any disease carriers is necessary. Cleaning and disinfection should be followed by a period of at least 3 weeks when no poultry are allowed on the premise. It's important to restock with Haemophilus paragallinarum- (chicken coryza) free stock. Vaccination may also be used as a preventative although serotype-specific (A, B, or C) vaccines should match the serotype of the infecting bacteria otherwise vaccine failure may be expected. Your avian vet can help you in this regard.
2. Separating the flocks for a month is prudent. A month is enough time to see if the young additions are ill.
3. Tylosin has a 0-day egg withdrawal. Please see here: https://vet.osu.edu/sites/vet.osu.edu/files/documents/extension/Egg%20residue%20considerations%20during%20the%20treatment%20of%20backyard%20poultry%202015.pdf
Oxytetracycline has a 5-day egg withdrawal. Please see here: http://web.uconn.edu/poultry/poultrypages/diseasefactsheet.html
The FARAD site is your best bet for this information but I've found it to be woefully incomplete, however, and so encourage you or your veterinarian to contact FARAD directly at the phone number supplied.
4. There are sites after sites discussing poultry management. Stick with the academic ones such as Cornell's: http://allegany.cce.cornell.edu/agriculture/poultry which contains a multitude of useful and vetted links. If you have specific questions for me, I'd be pleased to answer them but I regret that a thorough discussion of poultry managment is beyond the scope of this venue.