How much fitness you've lost isn't worth your time to think about. That's done. Your only concern is the future. In that future, try not to do that again. Indoors works fine if that's your only option.
Your program looks fine. If you're much over 50, I'd recommend dropping that 80% on Thursday down to 75%. Or better yet, do a lactate threshold test and base your zones off that, so more like 85% LTHR. On Friday or Saturday, depending on your response, you might try 30-45 minutes of relatively easy riding with one very hard effort of about 1.5 minutes. You might want to try a walk or brief run on Wednesday.
More importantly, you want at least 100 miles a week, preferably more, and at least 50 feet of elevation gain per mile if that's available. Climbing is the quick way to get fit.
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Results matter