Hi, again, MBear ...
OK, this whole law of attraction, manifesting, deliberate creation, et al., concept is still new to me as well. Anything I suggest is based on my best intepretation of what I've been attempting to learn for myself. Personally, I'm hoping that, as I make observations/suggestions for you, I will have some "a-ha" moments for myself, too.
Hmmm.... perhaps the real question is how to remove whatever may be blocking manifesting money.
For starters, based on various other sites, books, techniques, etc. that I've been studying, it seems that there are a plethora of LIMITING BELIEFS listed in your posts.
I've never been very good at making money.
It seems that I'm always running short or barely have enough.
I am especially short now, but for the most part, that's how it's always been.
I manage a budget well when I have the money to budget with; the problem is getting enough in the first place.
... I never have a hundred in cash at any one time.
I'm too short of money to be able to do that.
If I get a hundred dollars, I have to spend at least some of it right away--if I didn't, I wouldn't be able to keep up with basic necessities.
So presumably, that one's only for people who aren't that short of money to begin with!
In the Law of Attraction parlance, your vibration is one of lack. As you send it out, that's what comes back to you ... MORE LACK!
There are plenty of techniques out there for working with clearing limiting beliefs. EFT is one that I have mentioned before in a different thread on this forum. However, each person has to find what works for him/her.
The game that has already been suggested has been mentioned in many Law of Attraction exercises, including Abraham-Hicks, and seems to have piqued your interest. So, let's continue with that one for now.
I might be able to carry between twenty and forty dollars without spending it, but that doesn't give the "wealthy" feeling that a hundred would.
If one doesn't believe that s/he can have a monumental change, then it won't manifest due to that lack of belief. However, believing in and achieving smaller changes will build success, and belief, for bigger changes to occur. This concept/technique has been described elsewhere as manifesting "incremental abundance".
So, start right where you are with what you do believe you can accomplish. Carry around that $20 or $40 and practice repeatedly spending it in your mind. But, even more importantly, focus on the good feelings you have as you mentally spend it since they are what will raise your vibrations from lack to abundance. (By the way, I'm not sure that "abundance" and "wealth" are synonyms as far as this exercise is concerned.)
Personally, I don't know how well it works when you use Monopoly money. I guess some people have better success at bypassing their resistance, and it does work for them. For me, though, I have to have the real thing in my secret compartment in my wallet. As I understand it, a major part of the value of the exercise is knowing that you could actually spend that money in any of those ways if you chose to do so. That's why setting aside the real money works better for me ... because, at any time, I could make the conscious decision to pull that money out and have whatever it is I'm imagining buying. I have yet to find a merchant of any kind that accepts Monopoly money. (Besides, real money doesn't shred in the washer if you leave it in your pocket; it just gets "laundered".) 
I have done this exercise with varying amounts between $20-$50. Here's just one example of my own:
How good does it feel to go out and buy that "2 for $20" dinner at Applebee's? Focus on what it feels like to sit at the booth or table and have the luxury of a wait person come and take our order. What will we choose for the appetizer? How does it taste? What entrees do my dining companion and I choose? How are the meals presented? Smell the aroma of the food. Feel the satisfying fullness in my belly. How great does it feel to leave the clean-up to someone else?
The next step is yours. Will you play the game again and exercise your manifesting muscles?
