Is 1600 calories "gonna make me fat"?

I'll be frank, I can't tell if your exercise regime is actually hard enough.

A good rule of thumb is that to burn calories, you have to be sweating, quite a lot. Just strapping weights onto your ankles seems like a good idea, bur may not really be doing anything. I bet you could do 10 x 50 yard sprints 3 times a week and burn off more than the walks get you. Save time too.
Same with the weights, you don't specify how heavy, which leads me to think you don't have a goal, (other than the admirable one of looking good). Are you just swinging a couple of 5lb dumbells around for half an hour, or are you really breaking a sweat doing 60 x 65lb back squats in 10 min or something like that?

1600-1800 sounds doable for a lifetime, I get by with 2300 and drink a lot and eat loads of chocolate, so basically I'm not worth listening to, but I'm happy, thin(ish), and fit.

I'll be frank, I can't tell if your exercise regime is actually hard enough.

A good rule of thumb is that to burn calories, you have to be sweating, quite a lot. Just strapping weights onto your ankles seems like a good idea, bur may not really be doing anything. I bet you could do 10 x 50 yard sprints 3 times a week and burn off more than the walks get you. Save time too.
Same with the weights, you don't specify how heavy, which leads me to think you don't have a goal, (other than the admirable one of looking good). Are you just swinging a couple of 5lb dumbells around for half an hour, or are you really breaking a sweat doing 60 x 65lb back squats in 10 min or something like that?

1600-1800 sounds doable for a lifetime, I get by with 2300 and drink a lot and eat loads of chocolate, so basically I'm not worth listening to, but I'm happy, thin(ish), and fit.

Not true about the sweating a lot needed to loose weight. I don't really sweat and I've lost all my weight just by walking.

From a mathematical/physiological standpoint, you'll lose about an average of 1 lb. per week (roughly - everyone is different, but calories in and calories out is truly the equation for weight loss). Sounds like you know what you're doing, and are very well balanced and aspire for long-term results, so keep up your motivation!