Insulin will put size and strength on you in a fast amount of time. But from you listing your previous cycles, i don't suggest you using it. It's extremely dangerous and there is a huge difference between 10 ui and 50ui. You said you don't remember exactly how much test you ran, which will be problematic when you run insulin. Takes a lot of dedication and commitment id you want to pin slin. Doses have to be perfect, meals have to be perfect and most of all, carbs have to be tracked down to each gram. If you do decide to run it, the guides and info out there suggest using it after workouts. Imo, it's better to pin 15-30 minutes before workouts, chug a shake before going into the gym with appropriate carbs/protein, then sip on another shake during the workouts. Possibly even drink another one after. Having said that, slin is more of a size drug though. It will build muscle more than it will give you strength.
Idk much about crossfit but from what i've see , it requires a lot of cardio and strength at the same time. So If I were you, i'd run a 12-16 week cycle with 500mg/week test, 500-600mg/ week eq, and 60-80mg of anavar. That should increase your endurance, lean you up (if your diet is on point), and increase your strength. If you think you can handle it and need more endurance, look into EPO. But be warned, epo costs a lot, very little info on it and extremely dangerous