you're right about money management often getting talked about more than win % but that's because so often nowadays, there are plenty of competent cappers who still end up broke! and it's not because they can't pick winners, it's cause they can't manage their money.
they bet three plays on sunday at 1 unit and win them all, then they have a strong feeling on monday and bet 3 units and lose. 75% win pct. for the weekend and they only just broke even!
or they can pick winners long-term, but happen to hit a short-term losing streak and start to panick. then they start chasing their losses, doubling up for no reason, etc. etc.
you get the drift. but if you're only trying to bet NFL and make a living off it, you need to be betting about $5,000/game to make enough to live on!
it's pretty tought to make a living off just one sport, any sport (MLB aside, possibly)!, but let alone the NFL, the one sport that gives you the least amount of plays per year (compared to MLB, NBA or even NHL)
if you have a 54% win. over the past 5 seasons, that's really good. you probably have what it takes for the NFL at least (since i'm assuming that win pct. was with only part-time handicapping). if you could commit full-time each week, you should be able to raise that at least one percentage point.
why don't you pick another sport and give it a shot? NBA just started, let the first 10 games get played and then start handicapping. in basketball, the most important stat is the last 10 games played by each team (what happend season-to-date doesn't mean much, just stick with the last 10 games played or so for each team).
of course you'll have to learn how to weigh home and away scores differently and to subjectively factor in travel and team chemistry considerations, etc.....
unless you have a sports service you're sure than give you at least 55% or so over at least a few hundred plays per year (ideally 1,000 or more per year), i wouldn't recommend going at it full-time while relying mostly on them. remember too, you have to factor in how much it's going to cost you for their service?
most pros do at least 2 sports, some 3 or 4....and some do what i do too, often pay others to take care of the rest (like college FB + BB). that's how i can end up with over 1,500 plays a year, often many more. that's how we can end up with the big profits. it takes money to make money. you have to be churning your bankroll a LOT! a couple dozen, or even a couple hundred NFL plays won't get it done. and it takes a lot of wagers placed to both guarantee your long-term win pct. (anything can happen over a small number of plays) and to recognize large profits.