Hi I will take a stab at this
Use the dumas dogbone universal. Greatly reduces the alignment problems. Last I heard 3.2mm is the same as 1/8". You probably would be ok there.
None of the dumas props will work for your boat. Not if you want surface drive. A few Octura props could work here a X431 in plastic or the X427, X430, or X432 in metal.All of them are for a 1/8" shaft. The Graupner K series CF props would work really well here and don't cost too much. They would be 4mm threaded and would need a prop shaft with a 4mm thread on the end.
Your hull looks good .For strakes you could get some balsa or spruce square rods and sand one corner down to make a triangle . That would work. I have done that several times to make strakes. n.h.schmidt