I was struggling with a similar decision tree last year when thinking about b-school. The terms were slightly different for me, I think 8k per yr, but similar idea.
The two MBA programs nearby for me would take ~3yrs, and same for those within 4-5 hours (which I would do as weekend programs).
For you, it seems that you'll be in the 75k in 4 years. Assuming you stay in the same field, I'm not sure where you are getting 120k from. Outside of investment banking, consulting, brand managers, product managers, etc. at top companies, total pay for new MBAs will rarely cross 150k right out of school. Corporate finance post-mba is more like 115-135k base and bonus.
The issue with part time MBAs is that employers rarely reward you for it apart from maybe contributing some toward tuition each year. The real payoff is in the first few years post-mba when you jump in the pay scale to take a new role (for traditional full time mba). Advancement after that depends more on you since no one will care any more where you went to school.
For you, the assistance is solid, but the 2 yr commitment stinks... especially if you aren't moving into a different pay band and/or position. 2 yrs at 25k lower pay per year (assuming you could get 100k post-mba) doesn't justify the 28k they give you.
For me, the numbers just never made sense. In 2014 I was at ~90k all in as a junior financial analyst. I was considering an MBA, and it was borderline whether it made sense unless I needed/wanted to get into a different field where it's necessary (consulting, banking, brand mgmt, etc.). I decided to hold off and perhaps apply for fall'16 admission, but ended up getting promoted in 2015 to a senior analyst making ~110k all-in. At this point, an mba would ONLY make sense if I wanted to change fields. I should be at ~130k judging by what I estimate my company pays to post-mba candidates in finance, but I may be able to close that gap internally over the next 2 years somewhat, and also by switching companies if it makes sense then.
I ultimately decided that I would hold off on getting an MBA, and consider an executive/weekend MBA in the future if I felt it was holding me back from progressing.