Well, there are a few things it could be, and you've provided a number of clues to follow up. First of all, problems with your upper calf muscle (Gastrocnemius) has long-arch pain as a primary symptom. This becomes more likely when you indicate the arch pain does not respond to direct massage of the foot. Try working the upper rear calf muscle a couple inches down from the knee and slightly to the inside for starters, and do it sitting down.You need to spend a minute or two letting down the upper attachments of the Gastroc on the femur bone, to relax and soften the muscle a bit before digging in. You do this simply by bending the knee, and sitting down is a great way to do that. It also gets your hands in closer to your work.
If you don't get results after a few times a day, over a few days, of this therapy, try running without the orthotics. Many orthotic inserts, even prescription ones, have been found to be counterproductive. There are different foot types that respond differently to a given type of orthotic, even if it is custom made for the shape of your foot. In addition, from the head and upper body on down through the hips, knees, and ankles, there are differing gait patterns that require a matching foot plant. Your orthotics may not be matching the way your foot wants to move. Ditto for the shoe type, which may be too restrictive.
At this time it is important to point out that "plantar fasciitis" is really a catch-all description of a collection of symptoms. It is rarely a root cause or object disease, but subject to the many combinations of aforementioned influences on pain at the bottom of the foot. This is why it is so difficult to solve, especially by treating the symptoms alone. It can be like trying to find the entrance to a maze by working backwards from the exit - very difficult. When I mentioned the calf muscle, do you notice that I went far from the symptom to an apparently unrelated area? This is because of the phenomenon of "referred pain," in which pain symptoms manifest away from -sometimes far away from - the actual source.
Lastly, you mentioned toe cramps. Cramping anywhere can portend potential muscular dysfunction elsewhere, so there is a supporting cast of muscles to check that are once again, not in the foot itself. Your body has many redundant muscle groups, as back-up systems, to support each other's functions. While there are muscles near the toes for moving the toes, there are also more powerful muscles far up both sides of the calf that move the same toes via long skinny tendons. The tendons are tough and rarely fail, but the muscles they serve are frequently at less than 100%.
If your toes are cramping upward, start by working between the bones near the top of your foot, just below the ankle, and gradually work your way down, still between the bones where the muscles hide for safety. Now move up to the outside center of your lower leg (shin-splint area), where deeper muscles control the toes. You may be able to find exactly where they are by extending your toes upward off and on, and feeling the shin for the flexing muscle as you dothis, in order to locate it. This is especially important if you have difficulty lifting the toes to clear the ground or stairs when they are cramping.
If your toes are cramping downward, sometimes just rolling a golf ball under your foot will help, but up the back of your calf slightly toward the inside are the small toe flexor muscles that can lock the toes into a cramp (big toe muscle toward the outside, on the fibula bone - yes, they cross sides for leverage). Once again, you can find them by briefly flexing the toes downward while probing the rear calf with your fingers for the flexing muscle.
That's probably good enough for starters, although there is more to explore. Personally, I got better results by removing my arch supports, which were starving my plantar muscles of oxygen-rich blood flow, and replacing my orthotics with a quarter-sized plug of mole-foam stuck under the ball of my foot, underneath the insole. This can correct a common foot motion error, and won't hurt to try.
Don't forget that cramping and muscle function of all kinds benefits from proper electrolyte management, which for many (Westerners especially) involves greater intake of magnesium, best sourced from dark leafy greens. Iceberg lettuce is little more than a vehicle for dressings, unfortunately. Potassium from oranges, bananas, etc., can help too. Sodium and Calcium are generally well represented in our diets, but it doesn't hurt to check. Make sure you are getting some unfiltered sunlight at mid-day to assure natural Vitamin D production in your skin, or anything else your doctor recommends if you are deficient like most of us this time of year. It will improve muscle function across the board.
Perhaps the most important clue, is that you have been gradually increasing your mileage, and you hint that your pace may also have picked up. Both of these together, can make your legs surrender long before your will to run has flagged. You will adapt in time, but don't run, at least not so aggressively, through injuries, and have patience. Most people, if they stick with it, continue to improve for 10 years or so after they start running, regardless of age. Besides, there is recent medical evidence that speed and mileage are not a good combination for the heart long term. It's better to run short and fast together, and if you must run long, to take it easy.
One thing you did not mention is the kind of footwear you use the rest of the day. Elevated heels will aggravate, even cause, the symptoms you describe. Good luck troubleshooting this problem. The community here will be looking out for you, ready to celebrate when you succeed!
Here is a link to a popular interactive muscle troubleshooting tool...
http://www.getbodysmart.com/ap/muscularsystem/footmuscles/menu/menu.html
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