Heat rising then dropping is usually an intermittent thermistor problem, if it's properly broken it usually doesn't heat at all. I think you may be lucky and can fix the thermistor just by recrimping the connections. Look this up on the forums, it's a common problem and covered pretty well.

Is the acrylic properly broken, or just cracked (and still functional)? This is also pretty normal either way. Consider replacing the acrylic part with the printed "lawsy mk5" extruder, this is easier to use and not susceptible to cracking in the same way. Again, a common modification, plenty of help here on the forums.