*[Fleurons][1]* means here the ornament in form of flower located on a crown, like a laurel wreath.

*De foi trempée* is a poetical inversion. Standard French would be *trempée dans la foi*, i.e. steeped in faith. 

*...épopée des plus brillants exploits* is more a superlative than a comparative. The deeds are not compared to anything particular. That just means something like "...an epic made of the brightest achievements".

You might also have trouble with *ceint* which is a rare verb in French ([ceindre][2]), meaning encircled. Derived words like *ceinture* (belt) are common though.


  [1]: http://www.cnrtl.fr/definition/fleurons/1
  [2]: http://www.cnrtl.fr/definition/ceindre