I won't get into the flight arrangements since you've already had advice on that, and it is what it is. You'll survive however you get there. I have abandoned TPACS on UA for the most part, and prefer Asiana via ICN as one poster mentioned above, especially in economy class. Focusing more on the destination and your first two questions:

1) Nothing is required. As for recommended: Assuming you had your childhood shots, you should make sure your tetanus booster is up to date. Hepatitis A is a must, and usually it takes two shots to do the full series, but even the first shot is going to give some protection. I would also advocate for Hepatitis B for long-stayers due to prevalence of a huge part of the Chinese population being carriers. A and B can be given as a combination shot. If in the USA contact your local health department, who is likely to be cheaper for these than a private doctor or travel clinic. If in a country with socialized health scheme, that would be your likely first stop. I wouldn't worry about anything else such as Rabies or Japanese encephalitis. Typhoid is one that's on the bubble--it's not common in Beijing or northern China and I let mine lapse years ago. But if traveling a lot to SE Asia, India, etc during the next couple of years, might be one to get.

2) I would pack into your checked luggage, enough clothes to get you started at least through the warmer months, especially if you are a larger size or not built like an Asian guy. Also shoes and socks (don't laugh, IMO Chinese socks suck). No need to go overboard though. There are plenty of crap markets that sell crap T-shirts and casual stuff so I wouldn't worry about that, but bring your business clothes and accessories. While you may hear people here talk about tailors and that's true, for a new job in a new place, you're likely not going to want to deal with this sort of stuff nor have time for tons of shopping, at least for the first three months.

Toiletries. Bring a 2-3 months' supply of your favorite stuff of the following items:
--Antiperspirant. Deodorant is available but brand choice is slim. Antiperspirant is not as available and very limited on choice, and expensive. Bring some.
--Sterile Saline. If you wear contact lens and use pure sterile saline for any reason, bring several bottles--in all my years here, this has never been available in the PRC. (Name brand disinfectant solutions and all-in-one solutions, yes are available).
--Specialty toothpaste if you use, such as Sensodyne. It is available but costs a fortune. Standard toothpaste and care stuff is available, as are Sonicare electrics.
--Sunscreen. Bring a bottle for the summer. Limited choice and expensive in Beijing, at least for reliably-formulated products.
--Insect Repellent, DEET-based. Ditto. Do not bring an aerosol can (goes for all other products as well). Get a pump spray, tape the top to avoid wiggling open in transit, and double-bag in plastic or a tupperware container for travel.
--Aftershave only if you have a strong favorite, until you find something locally-available that you like. If you bring, make it a small non-glass bottle.
--Specialty and medicated shampoos only if you use. Normal stuff available in China, and when you see what Beijing's hard water does to hair and skin, likely you'll need to experiment with new products anyway.
--Q-tips. Chinese cotton swabs suck. Big time. No country can ever have aspirations of taking over the planet if it can't produce decent swabs. But I digress....
--Basic medical kit with OTC products acetomenaphen (tylenol, panadol), aspirin and baby aspirin, stomach acid reducers such as Zantac, pepto bismol tablets, triple antibiotic cream, hydrocortisone or benadryl cream, good quality bandaids. These things are a pain to source locally. There might be local alternatives but it's really just easier to visit a familiar store in your current location and pick up a few things--they don't take up much room and when you need them in everyday China life, it's nice not to have to go on a fishing expedition in a Chinese pharmacy.
--A supply of any ongoing prescription medicines you take, get your doctor to write for 90-day supply if you need to stock up before leaving. After you arrive and get settled, you'll have to establish a personal supply/logistics chain to get refills from home to China, preferably a friend or colleague coming over. Do not have this kind of stuff mailed to China. All prescription meds need to stay with you in the carry-on luggage during the trip over. Some Western medicines are available in China, of which some are genuine and some are fake or questionably safe versions.
--Any professional books that are absolutely essential to your work. If not numerous, these might fit in your travel bags. If weighty or numerous, have the company pay for shipping them separately or possibly pay for another additional bag to accompany you. While additional bag fees seem expensive, in fact they are a good deal when you look at the cost/hassle of shipping packages to China and having to deal with inbound Customs Clearance.

Travel:
--No electronics (except chargers) in checked bags. No exceptions if you ever want to see them again. Your personal stuff like laptop, tablet, phones, Ipods, camera, etc. need to stay with you in your carry-on. If the company is requiring the transport of a lot of business stuff, have them ship it corporate by Intl FedEx and let them take responsibility for insuring, customs clearance, etc.

--Don't waste carry-on space carrying food. Put anything you feel you need in your checked bags but personally, I'd eliminate this category entirely. Also eliminate if you're from a 110v electric country like USA or Canada: household electrics like hair dryers, kitchen appliances etc. Best obtained locally.

A year is not a long time....try to do without as much as you can and find substitutes for the rest.

And...Welcome to FlyerTalk and the China Forum!