In Asia, where charcoal cooking has been used for many thousands of years, starter charcoals are perpetually maintained to start slow-burning hardwood indoor fires. The beauty of your small olive pit coals is that they fit snuggling together, slowing air intake *once they are thoroughly ignited*. That's the key. You mound them with your starter coals, keeping them loose enough for air intake.
You're going to have to be a bit inventive on how best to maintain your perpetual starter coals. Think about the physics of banking a fire for clues:http://www.ehow.com/how_4714687_bank-a-fire.html
Be prepared to tend your starter coals daily because you will need to add a piece or two every few days. Your use of the clay pot to protect your stove from rain was clever. Use that same approach to build yourself a little insulated and fire-proof coal saver. Recycle your coals as starters, just as has been done for tens of thousands of years.
By the way, your wire mesh grate not last long because of water/heat oxidation of the metal. Tim mentions use of a cheap clay grating that may be a more long-lasting choice of materials.
Once you have mastered management of starter coals, turn your attention next to Japanese methods of fire tending. Google it. The Japanese and Koreans have recipes for various types of indoor fires - combustion mixtures, placement of coals and timing in managing your little stove is an art in itself.
Well worth the practice, because it gets you out into your lovely garden for fresh air, tenderly tending hot water preparation as you meditate on your selection of tea and it's qualities.
Therein lies the zen simplicity of heating water for tea: chanoyu is the way of Water for Tea.