FTP and training programs, but confused

Try to summarise this and not make it an essay.

Had some time off, Christmas/New Year before Christmas, was having trouble completing some workouts specifically on the Gran Fondo plan, so started thinking my FTP was maybe not accurate. Had 10 days off on a resort holiday and figured I would get back to Zwift when I get back home and settled. On my holidays I use the gym the indoor bikes usually twice a day, morning and evening. Had a minor issue not feeling very good one morning put it down to alcohol (all inclusive resort) + food.

All up probably had riding but not structured for about 3 weeks, just when I had time when I got back I was mentally prepared to do an FTP Ramp test and a reduced FTP and get back into a program like Build Me UP which I really enjoyed last time.

Did the Ramp test this morning, my FTP went up 3 watts to 257, I am so confused, can maybe over training and bad diet (probably mu weakest area), I am 49 be the reason for my struggles. When I got back I basically had 4 days at work no riding and I have been eating very well, minimal chocolate, no alcohol and I have been feeling pretty good the last 2 days.

My plan is to start Build Me up tomorrow with the zone benchmark ride and see how I feel and then go from there, I really did enjoy Build Me Up last time and I got a LOT of benefit out of it, it really improved my weight (with good diet) and overall fitness, does this seem like a reasonable plan ?