[Marcus26]

Do not buy off eBay. It's like buying a custom suit off eBay, it needs to be fitted to you.
I'm not sure where you got all your letoff calculations and holding weights from, sounds like someone has been telling you rubbish.
Compound bows today come in basically 2 configs. 65% and 80% letoff.
The 65% ones are generally hardcore target bows. The 80% ones are usually more all purpose bows.
Some, like many Bowtechs, allow you to adjust between those values.
Others like the Hoyts let you change via modules (and a bowpress)

Now you will get some debate on which is better, but in my experience a 75-80% letoff will be easier for you to get the hang of quickly so would be my recommendation.
Don't fuss about holding wieght. These are elite archer concerns.

Spend big on your release aid and USE IT CORRECTLY by squeezing it slowly and not making it fire. This is the best advise you will ever get.

So what's best for you? Being an adult male you will put on the strength fast, so go a 60lb bow. I would suggest something with modules like the Bowtech or Hoyt bows. The Guardian is a great all rounder and the Commander is also excellent.
Both bows will go lower than 50lb so you should grow with them well.

Get fit out by a good dealer like CBA. Don't buy off eBay or off a club member because at last the shop is professional and will do the right thing by you.