How to calculate the power level of a Commander deck?
Power level is very subjective, and its main purpose is to communicate gameplay expectations.
I personally think that trying to create a very refined algorithm for grading power levels misses the point of what the power level is trying to achieve.  Power level is based mostly on comparing decks to each other.
Because Commander is mostly a casual, multiplayer format, power level is simply a discussion to help maintain player parity to ensure interactive and enjoyable gameplay.  It's to prevent someone's janky Pirates win with treasure deck from being completely obliterated by a well-tuned Prossh Food Chain combo deck.  While both those decks are playing Commander, they're arguably playing different games.  The power level is a discussion tool to manage expectations and make sure no one feels left out of this long, multiplayer game.
To that end, the parameters I've heard for determining power level are much less specific than the ones you've posited in the question. The concepts I use to estimate power level are as follows:

Raw power of win conditions
Consistency
Speed

Some of your criteria in the question fall into these broad categories.  For example, the presence of Commander staple ramp cards help improve both the consistency and speed of the deck.  Immediate win-conditions like Expropriate or Craterhoof Behemoth have good raw-power.  Having a single combo that is easily disrupted by your opponents' removal lowers the consistency of your deck.
Comparing decks is just making sure that games are fun and reasonably competitive instead of being one player playing solitaire and everyone one else just watching.  So I wouldn't worry about getting the exact numbers in your rating system as long as the decks are close.  That being said, my 0-10 rating system, that I based on advice from The Command Zone (a podcast about Commander), is as follows:

0-1: It's hard to consciously bring yourself to make a deck this actively bad unless you're going for an off-beat theme like &quot;griffon tribal.&quot;
2-3: These decks might be a jumble of rares (and not necessarily good ones) that someone had in their collection.  The commander exists to provide the color identity needed to play all of these favorite cards, even though many do not synergize with each other.  Consistency is typically low because there is no coherent idea for the deck.
4-5: Most of the Commander pre-constructed deck are at this power level.  There are some themes in the deck, but maybe the deck just plays slowly due a lack of ramp.  Possibly there are too many ideas going on at once, or maybe the win-conditions are just not very powerful.
6-8: These decks have a very clear game plan.  They are pretty efficient and/or flexible.  Research and refinement of deckbuilding is likely.  Upgraded pre-cons and decks that have gone through experimentation and updating typically are around here.  The financial costs of these decks can be higher due to the expense of consistent, faster mana bases or sought-after singles that are high impact.
9-10: These decks are built to win.  They are competitive-tier (CEDH) decks that are very fast and very consistent.  Often, these decks use expensive cards (like Mox) to help speed up the deck even more.


Based on your brief description of your Samut beatdown deck, I'd estimate it at about 5 depending on how consistent it is.  The strategy sounds a bit fragile because it appears all-in on combat and lacks card draw, but it sounds like it has plenty of threats and ways to deal damage.