Solutions :

3-letter words (1 point): 37

BIO; BIT; EIK; ERE; EST; EVO; IOS; KET; KIP; KIT; OES; OIK; OSE; PER; PET; PIE; PIT; PRE; REI; REO; REP; RES; RET; REV; SEI; SER; SET; SOT; SOV; TES; TET; TIE; TIP; TOE; VET; VIE; VOE.

4-letter words (1 point): 53

BIER; BIKE; BIOS; BITE; BITT; ERES; EREV; EVOS; KEST; KETE; KETO; KETS; KIER; KITE; OVER; PERE; PERT; PIER; PIES; PIET; PIKE; REIK; REOS; REST; RETE; RETS; SEIK; SEKT; SERE; SETT; STET; TEST; TETE; TETS; TIER; TIES; TIKE; TIPT; TOES; TOIT; TOSE; TREK; TRES; TRET; VERT; VEST; VETO; VETS; VIER; VIES; VITE; VOES; VOTE.

5-letter words (2 points): 39

BIKER; BIKES; BITER; BITES; BITTE; BITTS; EVITE; IVIES; KITER; KITES; OTTER; OVERT; PERES; PERTS; PETER; PETRE; PETTO; PIERT; PIETS; PIKER; PIKES; PIVOT; PREST; RESTO; RETES; RETIE; STERE; STOIT; STOVE; STREP; TEREK; TERES; TERTS; TIKES; TREST; TRETS; VERTS; VOTER; VOTES.

6-letter words (3 points): 14

BITTER; PETRES; PETTER; PIERTS; PITTER; PIVOTS; PRESTO; RETEST; RETIES; SETTER; SOVIET; STOVER; VETTER; VIBIER.

7-letter words (7 points): 6

OVERTIP; PERTEST; PIVOTER; PRETEST; STOITER; VIBIEST.