need help again

1. Nope, if Dogmeat dies, he's gone. There are other followers though. Most of them, with the exception of Charon need you to have specific Karma requirement for them to enter your party. To get Charon, ask the owner of the Ninth Circle in Underworld about his contract. He will sell it to you for 2000 caps (1000 if your barter is high enough) or you can kill a certain employee from the Inn in Underworld. Either way, you'll get Charon's contract. He will kill the owner of the Ninth Circle (Get his key off of him so you can raid the inventory) and then join your party, reguarless of Karma. Here are the others and their locations and karma and other requirements:
Good Karma - Fawkes (Complete the quests "Finding the Garden of Eden" and "The American Dream" and free Fawkes from her cell during "Finding the Garden of Eden". You'll meet her at the end of "The American Dream" and if your Karma is right, she can join you then. If not, she'll be wandering around just outside of Underworld, inside of the Museum of History.) and Star Paladin Cross (In the Citadel.)
Neutral Karma - Butch (Complete the quest "Trouble on the Homefront". He then can be found in the Muddy Rudder bar in Rivet City. Possibly the weakest of all companions) and Sergeant RL-3 (Found wandering around the Robo-Co factory, following Tinker Joe. If Joe dies, he cannot be obtained. If you meet the karma requirements, you can buy him for 1000 caps off of Joe.)
Bad Karma - Jericho (Found in Megaton. Must be payed 1000 caps before he will join you.) or Clover (Found in Paradise Falls. Bought off of Eulogy Jones.)

2. Sort of. At the end of the quest "The American Dream" you will be made an 'official' member of the Lyons Pride. All it really does is give you a choice of getting full Recon or Power Armor in perfect condition, and access to the final quest of the game, "Take it Back!"

3. Should be North-Eastish of Tenpenny Tower. It's called Fort Independance. It has an unmarked quest where you can trade Sensor Moduels, Power Armor, Enclave Armor, Telsa Armor, Laser Rifles, Plasma Rifles, Plasma Pistols, Scrap Armor, the Alien Blaster, and Alien Power Cells (Don't do the last two, as the former is one-of-a-kind and the latter is very rare) for 5.56mm rounds, Frag Grenades or Stim Packs. Once you've traded enough stuff, you'll be granted access to Fort Independance without getting attacked by the Outcasts. Inside you'll find some minor loot, a Nuka-Cola Quantum, and an armory with some weapons, some ammo (Including some random amount of the very rare Alien Power Cells) and the One-of-a-kind weapon, the Miss Launcher. There is no other Brotherhood base close to here to my knowledge.

4. East-South-East of Megaton I believe. It's not really close to Andale at all. The Enclave Soldiers and officers are part of the Enclave, obviously, and part of random research camps you find after completing the quest, "The Waters of Life" (Or "The American Dream". I forget which.)

Well, loony answered all your questions, but here's some useful info relating to your first question. If you get the Broken Steel expansion, your level cap raises to 30, plus you get new perks. One of the new perks (the name doesn't come to mind at the moment, sorry) allows you to get another "Dogmeat" if the original one dies. You see, according to the perk's description, Dogmeat had puppies, so if he dies, another dog will be waiting for you at Vault 101. I'm assuming you'll get a new dog each time the previous one dies, but I'm not sure how many times you can receive a new dog.