If you are going to race downwind slalom, a fin around 38 cm with the 7.5 would be good. If you just free sail or figure 8 slalom where better upwind performance is needed, then a 40 or 42 would be fine.
My 111 came with two drake fins, a 38 and a 44. Both had bad spin out problems so I bought a Tectonics Tomcat 42 to cover my 6.6, 7.6 and 8.4. It works well with all three sails. I tend to like larger more powerful fins and don't find the 42 too big for my 6.6. I don't race slalom very often.
Your 44cm fin could be a little large for your 7.5 and your weight, but it should work OK if not overpowered in light conditions.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.