A reward is anything your dog finds rewarding. We use food mostly as it is a Primary Reinforcer.
Secondary reinforcers are things like praise, toys, play, the environment and so on
I would always suggest a good fitting harness with 2 points of contact if possible. A good length of lead with 2 clips.
Ask me for recommendations and steer clear of the no pull harness and head collars. These just make your dog uncomfortable and are aversive.
Consistent training will nail that loose lead walking
While a group class would not be beneficial for your dog at this moment in time, we can work on their emotions in private 121s. We can also cover the same skills that will be taught in class.
Dog training has evolved and in line with modern science based research. We have known how dogs learn for many years, it just needed the dog trainers to catch up.
Cue has replaced the word Command because it is amongst other reasons about the relationship and partnership between yourself and your dog. We can use Visual and Verbal cues
Dogs are never too old or young to learn. There may be many ingrained habits to unpick and retrain in an older dog.
But surely any positive interaction including fun, games and enrichment is beneficial for all dogs regardless of age