A factual assumption in the question
IS WRONG.
OP writes:
"they've been investing in me tremendously by..."
that statement
IS INCORRECT.
The company has been paying a pittance on side benefits such as gym membership, the very cheap training mentioned, and free donuts, specifically to trick gullible young employees in to working hard for them for low money.
In this situation employees are literally being tricked in to an "I am obligated to the company" mentality for an unnecessarily low salary.
This is an explicit, widely-known, feature of Silicon Valley culture and software culture broadly today.
Founders and financial-level management in companies literally sit down and explicitly discuss and plan what sort of nonsense like ping ping tables and "certifications" they can spend a tiny amount of money on, to trick folks in to working for a low salary.
This is the norm in almost all software companies or companies with a software function.
It is a standard, explicit, feature of the industry today.
In Silicon Valley there are literally consultants who analyze this donuts-and-certificates nonsense to decide what is the best "pennies on ping pong, rather than tens of millions in salaries" for maximum effect.
You can literally see new ideas in this field being tried from year to year:
"Flexible! vacation time! you decide!" is a recent idea a consultant came up with, and you see it now frequently. "A budget! to buy your own gear!" ... "home valet service!" ... "work on open source Thursdays!"
Etc, etc, etc.
In a few years when OP is leading a team, OP will literally be talking with the Founders and accounting side about how to keep Young Timmy and Jenny on the team - without, of course, jacking up their salary. Will Timmy will respond better to a $200 "certification", casual! Fridays, a slice of pizza, a trip! to London, or a new! clicky gaming keyboard ... instead of jacking up Timmy's salary 40k.
Because programming is so expensive, it's become standard "Silicon Valley culture" to have idiocy like "free lunch" and (literally!) ping pong tables, in an effort to keep contract prices down.
The actual statements of OP such as:
"I feel very grateful..."
.. literally make me feel sad, because someone is being CONNED.
Software is often an incredibly high value-generating function.
It's nothing for a programmer to generate a hundred times the value they are paid in a year.
If feeling grateful, I would urge to rethink that, as one's entire future depends on it.
To simply answer the two questions:
"would it burn bridges to leave...
Of course not.
30 seconds after you are gone nobody will know or remember your name.
Regarding their comic spending on donuts, ping pong tables, $200 training courses, and Friday Pizza, it means nothing. Nothing.
Founders sit down explicitly and discuss what such idiocy they can spend a few pennies on to avoid paying money to programmers.
If thinking about how it will look "on your resume" in 10 years:
Once your career is underway, programmers typically don't even type in that "first job" since it was so lowly paid. You'll likely never even mention it again.
"First job syndrome" is a serious problem. Any programmer who took forever - years - to move along from their first job, you wonder why. Did they not get offers? Were they comfortable in a rut working for low pay?
"would it be "disloyal" to leave...
This concept is not a thing.
If the company was losing one dollar a week on someone, they'd be instantly let go by the corporate machine of accounting and money, as a mechanical action, an arithmetical decision with no human involvement whatsoever.
(Far less "loyalty" ... what? from whom? how? There is not even a mechanism for such a thing.)
If the company happened to go bankrupt, you'd get a form letter from some liquidators stating what date you were terminated and how much money you have lost.
If a new team lead comes on with her own crew you will be let go without your name even being mentioned.
The notion "business is business" really doesn't cover the situation strongly enough.
--
If one is looking for negotiation language, it's very simple because you have ALL the power.
Steve, as you know I've passed that "first job" stage. I am now regularly offered { insert figure, say $40,000 } more than I'm currently getting. What to do?
Negotiation is trivial when you have ALL the power.
Just follow the basics: be polite, ask questions. If they don't send over what you want
Understood, is Friday ok for the company as a last day?
Another important point...
"... these new tools bumps my salary potential up by at least 50% increase. ..
OP is stating that the "training" given has bumped OP's earning potential by 50%.
This is wholly wrong.
100% of talented programmers, make a low wage the first year or so, then their wage skyrockets. It is an absolutely standard feature of the business. Any specific hokey certifications or specific "training" is wholly unrelated.
Every programmer, every month of their career from start to retirement is constantly aggressively learning totally novel technology. The everyday nature of programming is research-level learning. This is an obvious given of "being a programmer". Languages, platforms, paradigms change constantly. If the company in question did or didn't offer a few dollars in "certificates" or "training" ... makes no difference whatsoever to the fact that the OP (like every programmer) is constantly "worn out on learning" as a matter of course.