Travelling to Croydon after capping my Oyster card

I have moved to Croydon and I frequently find myself having to travel home after my Oyster card has been capped for lower zones, e.g. zone 1-2 or zone 1-3, and would like to confirm if I am using my Oyster card correctly. My Oyster card has a National Railcard discount.

11 March:
I travelled from Willesden Green to East Croydon (£4.15), East Croydon then back to Willesden Green (£4.15), Willesden Green to East Croydon again (£1.85), East Croydon to Clapham Junction (£0.00) and Clapham Junction to Willesden Green (£0.00), capping at the zones 1-5 rate.

12 March:
I travelled from Willesden Green to King’s Cross St Pancras only (£2.05).

13 March:
I travelled from East Croydon to Willesden Green (£4.15), then from Willesden Green to East Croydon (£4.15).

14 March:
I took a bus (£1.75), then train from Streatham to Seven Sisters during the evening peak (£5.20 to reach the £6.95 zone 1-3 cap), then Seven Sisters back to Victoria (£0.00 as the cap was reached). Then I made an OSI dance by tapping in-out-in at the National Rail gate, and travelled back to East Croydon (£2.90, railcard off-peak fare).

15 March:
I took a bus to work (£1.75), then another bus after work (£1.75), train from Brixton to Ravenscourt Park during the evening peak (£2.40 to reach the £5.90 zone 1-2 cap), then Ravenscourt Park back to Victoria (£0.00 as the cap was reached). I switched to KeyGo to travel from Victoria to East Croydon.

16 March:
I received an automated refund of £1.00 on my Oyster card at the moment I touched on a bus.

My question is that, was breaking the OSI at Victoria necessary on 14 March and 15 March? If I didn’t break my OSI at Victoria, would the full Seven Sisters or Ravenscourt Park to East Croydon fare be charged instead of Victoria to East Croydon only?

Also, what is the reason of my £1.00 refund as well?