- your issues sound like they mainly stem from 2nd level components that dont have the features/refinement of quality Shimano products. Fall out of alignment just from bumps? No ability to adjust cable tension at the RD?
- 5600 shifters are 4 generations old at this point. I would not spend time painting the plastic. If the hoods deteriorate, maybe you can find a replacement?...but likely just switch the shifters at that time. If they shift well, I would take 5600 external cable shifters over your Micronew(and I have owned 4 pairs of drop bar micronew/microshift shifters so this isnt just ignorance).
- the different shift process for Shimano vs Microshift simply is not difficult to adapt to. Ive read some people cant handle it and I honestly question what is happening in their minds that they cant successfully move a couple of levers. Point is, those who cant manage to adapt seem to be in the very small minority. I wouldnt let this weigh much on you.
- if you are concerned about a different style of shifting, the Sensah is different from Microshift too. Just keep that in mind.
- if you switch to Sensah, itll be cool that you will no longer be using blatantly ripped off shifters.

Personally, if I were trying to save some $ and create a wide range bike, I would go with the Sensah Team Pro shifters that are 2x11 and pair them with some Shimano derailleurs. That would be 2x up front so the crankset would need to be changed to a sub-compact model thats 46/30. Toss a GS shaped RD on and an 11-40 cassette with maybe a roadlink or longer b-screw if needed. It would save a lot of $ on the shifters and give you a Shimano RD in back.
...or just take the stuff you have right now, get rid of the RD and use a Shimano RD, and run a double crankset since you already have 2x shifters.

But hey- I am clearly in the camp that views 2x as more versatile and simpler for planning how to set up a bike than 1x.