Welcome! Use a pot that just fits the healthy roots snugly. If you have to cut off a lot of dead roots you might have to use a much smaller pot. You want to match the pot to the roots, not the size of the leaves. You do not want to over pot the plant. Use a pot with a lot of drainage holes. I do not recommend planting it directly in a decrotive container. Use a plastic pot or a terra cotta clay pot. Do not use a glazed clay pot. You can put the plastic or clay pot in a decrotive container but make sure there is air flow to the roots and between the two pots. If you have low humidity and the pot dries out fast I would use a plastic pot. But then again if you like to water a lot clay pots dry out faster. It's up to you.
You want to use a bark mix. Lowes or Home depot carry a brand called Better-Gro special orchid mix. It consists of fir bark, horticulture charcoal, and sponge rock. Do not use the Miricle Grow Orchid Mix. It is a peat mix and is too soil like for most orchids. When you get the mix soak it for at least 24 hours. Longer is actually better. New bark doesn't retain water as much as older bark.
When you repot and look at your roots you will see if you are over watering. If a lot of the roots are rotten and squishy then you might be over watering. A lot of people use a wooden skewer to help them know when to water. You can use a skewer you use for kabobs. Put the skewer in the middle of the pot and always keep it there. You can pull it out of the meadium to check when it is time to water. You want to put it in the middle of the pot because the medium in the middle usually dries out last. Even if the top of the meadium is dry there might still be enough moisture in the middle of the pot. If the skewer is dry then it is time to water. If it is wet, don't water. If you are not sure if it is dry enough you can always wait an extra day to water. Over watering is worse than under watering. You can fix under watering easier than over watering. People kill orchids more by over watering than under watering.
The leaf drop could be normal. Phals will shed their bottom leaves every once in a while. If it is happening a lot, it isn't normal. Over watering can cause leaf drop. If you are concerned about humidity you can place your orchids on a tray full of pebbles with water in it. Make sure the water isn't touching the bottom of the pots. You can also use a humidifier.
Everyone has their own preference on cutting spikes. If it turns brown it is time to cut it off. I cut my spikes all the way off at the base of the plant after all the flowers fall off. I don't wait for the spike to turn brown. Some people cut the spike to the next node on the spike to try and induce a second blooming off the old spike. Some Phals will branch from the node and some won't. I don't like to let my plants do that because I want them to rest and put their energy into new leaves and roots. I find that if you let them branch the flowers are smaller and there are fewer of them. My personal opinion is that it is healthier for the plant to cut the spike all the way off. It is up to you though. But if you find that your plant has a lot of root rot it would be better to cut the spike all the way off. You want the plant to put its energy into roots in that case instead of blooms to save the plant. I'm kind of worried about your plants roots because you said you are an over waterer and the pot it is in doesn't have any drainage holes. I would get it out of that pot ASAP.
There is a great thread called the Phal Abuse Ends Here. It has a lot of information on Phals bought from grocery stores and big box stores. It is long but is worth reading. I recommend reading it.
http://www.orchidboard.com/community...ends-here.html
I have a hard time finding pots I like around where I live so I buy them online. I don't have a store that carries many orchid supplies. Like I said Lowes or Home Depot has a decent bark mix but I usually don't find the clear plastic pots that I like at my local stores. There are many online orchid supply stores. There is Repotme.com, Kelly's Korner Orchid supplies, and Tindara's Orchid Supplies to name a few. I really like the slotted clear plastic pots. At least one of these stores carries them.
Good luck! If you have anymore questions don't hesitate to ask! You are going to love Orchid Board!