I had my very own modified version for about a year, your unit is certainly the "in-betweener" version before the Imag 3 came out. Dim light through the chamber means a thin layer of silicone rubber seal under your chamber, a Christmas-tree lightshow means absolutely no seal. There is a hole where power and thermistor wires entering, so you get the air coming through all over from the place, including PCB and battery - which is a controversial subject, but IMO posing no real threat - as thermal exposure is minimal to nothing here, and solid pollutants should get stopped by many obstacles (including your load) if there is any. A bit of a very unlikely lead or plastic dust would not do any harm to your respiratory cavities anyways
Body does a good job removing shit, unnecessary to panic. Your restricted airflow is actually somehow normal, there used to be 4 air-intake holes on the side, they got reduced exactly because there has to be a maximum amount set (assuming a general pull) for incoming cold air, otherwise the heater could not coop. A slooooooow pull can make a good pull
However they use two silicone profiles on both ends of the heater chamber, the one on the bottom is a sort of "bed" to keep the bottom of the chamber in place and open to air. This part during assembly can get somehow crumpled, and the wires can also simply bend into the way - just poor design really. Another note to add to your basics of vapour-knowledge, that ANY excessive humidity in your load can crucially reduce your amount of vapour, just as condensed gunk in the MP. It is also a good advice, to use an extra piece of strainer between mouthpiece and load, so no clogging will occur - this could make all the difference actually. The unscrew method for me worked perfectly, that was my main concern - you must make sure, that you unscrew the bit all the way to create a very tight fit on the top of your screen above the load! Either way, there are options out there, Imag worked well for me, though same applies to it as to all vaporizers - there is a learning curve, before you get all things right, but once done, its a bliss