Well, i think i may be able to help with a couple of things. first, you are using anthricite. if you were using bitumnious you would have better controll of the fire, few clinkers, but you would have black smoke and the coal would fuse and expand together in mid phase of burning.
1. clinkers, is fused coal ash directly due to the temp of the coal bed and make up of the ash more directly, the main culprit is iron pyrite content (the lower the better), most reputuable coal mines, even anthricite ones should tell you what the Ash Fusion Temp is or AFT, the higher the better.
2. when the coal "crusts over" which is odd in anthricite but still occurs with some coals; it is related to the free-swelling characteristics of a coal and this is generally much more pronounced in certain bituminous coals. however it is not a problem. Also this is NOT a clinker. the key to solving this problem is as you have already begun to discover - opening up the overfire air. however it is best to route the air though a pipe in the firebox first to heat the air and then to the fire rather than just through a door so that you ignite gasses more fully and increase the efficiency of your boiler, not decrease it.
3. when talking about the coal bed, providing you are using at least 1x1 coal or greater (and decent coal) you should have no problem making the bed of coals at least 20-28" thick and possibly half of that new coal. obviously this only works if your boiler is physically deep enough for that and it looks like yours is not. Make the bed deeper! not wider or longer. this will make your coal burning experience much more enjoyable.
4 when having problems burning coal in an easy manner also look to air issues, you have a forced underfire air system, so you should have very easy operation, however you don't. This may be partly due to air escaping around the coal bed when the blower is on and may also be related to problem 2. did you cement your firebrick with refractory cement? is the only place the air can go through the bed of coals?? the firebrick you have laying on the grate is that airtight?? if not, then it needs to be airtight. even a little air escaping around throught the firebrick and throguht he firebrick on the grate and other areas will cause signifigant problems; any air must go through the bed of coals, not around them.
5. your coal seems to be old anthricite, do you know how long it's been sitting around? i've seen anthricite in a small pile 30 years old that absolutely will not burn, even though it still looks fine, it has decomposed and oxidized away most of its btu content. obviously this has not happend to your coal, but the fact that it has been sitting around for a while, possibly unprotected from the weather may make your situation worse.