A few words of advice about Advice.

Be absolutely sure whomever you talk/email/forum visit with when getting advice knows your citrus is in a container. If the guy at the garden center says "well the container should be the same as in the ground, citrus can even grow in plain dirt. So xxxx product should work." run away -- as fast as you can and forget everything that person told you.

When I started I got so much advice (nursery, garden centers, friends, books, etc) I thought I retained everything quite well. However, I mistakenly mixed in-ground vs. container suggestions and the end result wasn't good. It took some mistakes and reading on this forum and the Container forum.

As has already started, you'll get conflicting advice about peat moss, special citrus soil, sand, wood chips, bark, gypsum, dolomite, compost, mulch, etc. Just remember, it's not like a stew, you can't take a little of everything that's "good for citrus" and have it work (that was my mistake). It's because container citrus are much less forgiving than in-ground.

Keep in mind there is a difference between "ideal advice" and "practical advice" and whether that's for the tree or the gardener. But you can do whatever you want. It's very easy to give canned advice using our own assumptions of the situation. You know your situation best and you'll learn more from the outcomes of your own decisions than you will memorizing what others are telling you.

Your Questions in Particular:

1) How big -- it depends on the rootstock. Lemon Drop I think is mix of kumquat / lemon that tastes a bit bitter sweet. You need to find the name of the rootstock, or at least search the tree and container for any labels/tags that may say "dwarf" or "semi-dwarf", if it doesn't say either it's likely not a dwarf and I wouldn't plant this tree in a container (making the entire thread moot) ;-) Ask where you purchased it for the exact name of the roostock to find out.

A rough estimate in container: true dwarf: 4-6', semi-dwarf: 5-8' depending on pruning.

2) Yes that 22" x 2' deep terra cotta container will ultimately be big enough. That's only a few inches smaller than a half wine barrel.

You CAN put your tree in that huge container, but the ideal method is to upgrade the pot size every year or so. If you do use your 22" container, it will provide more protection in the freeze, but know it will tend to "hold" on to more water than a small tree can use. But many people do it, you just have to be more careful watching your tree's health.

Other than that, I don't know much about freezing temps except for buying the frost blankets to cover it, watering deeply on cold nights, using lights, etc.

3) If you have "citrus fertilizer stakes" they are for in-ground and not containers.

4) The ideal: pluck off that fruit sorry :(, wait a few months until after the growing season, and then pot it in container a few inches larger than the current. Of course, fertilize and water until then.

Soil
Your soil choice in a container is critical. The technical stuff is about drainage, aeration, ph, etc. But practically because it determines how much/often to water, fertilize, and certain soils compact sooner than others, which means you'll need to replace it sooner. Using a good draining soil is even more critical if you put a young citrus in an overly large container.

However, short and simple: buy special Palm/Citrus soil w/fertilizer added (big box stores have it in 8 qt bags for about $6). You're probably fine with ONLY that soil. Add a couple inches of any mulch on top (except not directly on the trunk). Buy a citrus fertilizer in pellet form that say "contains micronutrients" on the front and follow the directions for using in container (about 90% of the directions is for in-ground, there is usually a small paragraph at the bottom for containers). And you're good for a year if watered well (over-watering will kill it quickly) and protected from the severe elements. This may not be "the best" but it's an easy task for beginners to keep the citrus healthy enough to buy you time you learning about optimal care requirements.

Re-potting and Roots
Lastly, I didn't realize the down-the-road work involved in containers. Not to scare you away, but be prepared for work every year or two: replace the container soil, upsize the pot, prune roots, etc. How often depends on the soil you picked above.

More Help
There is a TON of valuable information already here in these forums and the net. You will want to learn more than my long-winded advice can provide.

Search Terms: Caring for Citrus, Pruning Citrus, Fertilizer. There is a very good series of posts, albeit technical, titled "Container Soils - Water Movement and Retention" by Tapla--Al if you're inclined. http://forums2.gardenweb.com/forums/load/contain/msg010937265978.html?143

Caring for citrus is very standardized but there may be important caveats depending on where you live. That's why I didn't provide links for Citrus care. For example, I live in Fresno, CA and University of California Davis has excellent information about Citrus in California, even specifically where I live. There are different pests here, and the rootstocks for trees I buy may not be the same as in your area.

Have fun and hope you love citrus as much as I do!