ek’s on the right track, but if you’re coming out with more stitches/rows per inch, then you’ve knit too tightly (due to personal style and needle size). Since the rows are smaller, more fit in the inch…
And the row gage may be off, but how’s your stitch gage (sideways vs. up and down)? If the pattern calls for you to work so many inches long, then row gage isn’t usually as important ans stich gage. Your stitch gage will give you the propper side to side measurement, and if you’re working so many inches long, then the row gage shouldn’t matter too much unless there is a color pattern/shaping feature that is row dependent.
I really never wash and block my swatches though I should, technically, do it One of the reasons for washing and blocking is to get it flat and even so you can take true measurements, rather than trying to flatten out, say, curling stockinete stitch to take a measurement on while you’re ruler is in hand. Like I do One of the ways to minimize curling is to put a garter stitch border of 3-5 stitchs/first rows around the edge it helps keep it flat for you. When you take measurments, you have to carefully spread the stitches on the needle so it lies flat without streatching or bunching the fabrick, and that’s kind of trial and error art.
As for the washing bit, remember that washing yarn/fabric will invariably change its properties a bit as it interacts with the yarn. However, as long as you wash your finished product per the instructions from the yarn manufacturer, things should more or less work out all right wihout too much alteration to the finished product.
The felted marino shouldn’t affect things too much, though I have never worked with it so I can’t say that for certain.
I reccomend knitting swatches and switching needles until you get what you need, then unravel and resuse. The way I do it to keep from butchering the yarn too much is to knit with the reccomended needles for several inches, measure my gage, and if it’s wrong, switch needles on that same swatch and knit a few more inches, test gage, etc. This gives me a long swatch, but allows me to only unravel once instead of many times. You just have to make sure you knit enough inches to let the new gage fully take affect; an inch with new needles may still be affected by the gage just below it. I just pick up the new needles, and knit from the old with the new.
Of course, you could always get more yarn too… even if you have to order it and it will take a while to arrive, you can start with what you’ve got and use the new stuff to finish up with…