Solutions :

3-letter words (1 point): 42

ADS; DAS; DIP; DIT; DUH; DUO; HOT; HOX; HUT; IDS; ITS; KID; KIP; KIT; KOI; KOP; OIK; ORT; OUD; OUK; OUS; OUT; OXO; PIT; PIU; PIX; POI; POX; PRO; PUR; ROT; SAD; SUD; THO; TID; TIP; TIX; TOR; UDS; UPO; URP; UTS.

4-letter words (1 point): 26

ADIT; DITS; DUST; HOTS; HOUT; HUTS; KIDS; KITH; KITS; ORTS; OUDS; OUST; OUTS; OXID; PITH; PITS; POUK; ROTI; ROTS; ROUT; SADI; STUD; THOU; THUD; THUS; TIDS.

5-letter words (2 points): 14

ADITS; ADUST; HOUTS; OUIJA; OXIDS; PROUD; ROUST; ROUTH; ROUTS; SUTOR; THORP; THOUS; THUDS; TSADI.

6-letter words (3 points): 6

OUIJAS; POUKIT; STROUD; STUDIO; TORPID; TOXOID.

7-letter words (7 points): 2

TORPIDS; TOXOIDS.