I'm thinking the codes are for airfields and the numbers may be squadrons. Based on when these airfields were captured/made, it looks like this may have been from the end of 1944. Any information or direction would be awesome, I can take more photos if needed.
I can't see the legend. There should be something in the bottom right corner telling you what stuff is. Blue line = river, Red line = road, black line = railroad, white dot in black line= train station, black circle with black dot and compass points = prewar airport, Black circle = farmer's field airbase. Something like that. The pencilled numbers appear to be compass headings. Vectors from one airfield to another, or safe routing between AA emplacements, there are pencilled lines for each number, and a degree symbol. Some of the vectors are wrong, there are two for 111 degrees, and the lines should be parallel. Maybe a student pilot? The red crosses are part of a grid pattern.
I think the 301^o -121^o notations are compass headings for the line drawn on the map. They have the degree symbols, and it looks like that's about the angle it's drawn on the map relative to the grid lines. 301 - 121 = 180, so those are probably the reciprocal bearings of the line drawn.
Is your map printed on cloth with another map on the back?
I inherited a similar one from a great-uncle who parachuted into Poland circa late 43 (frontiers on the map date to September, '43) for intelligence work. It's clearly part of a series (both sides numbered 43, sheets E and F, notes on every margin about where they overlap with another sheet) so you may have a British version (I see from the RAF and War Office references.) of something from the same series, or one a year or so later.
Nothing in the legend of mine says anything about airfields and personal markings are limited to marking his parents' home town, so regrettably I can't help much with those.
I'm on my overnight shift right now so i've got nothing but time on my hands.
It looks like the fourth picture, which has Longuyon near the centre, has a black line with a black dot every so often. That black line is the border between Belgium and France. Longuyon is in France, Virton is in Belgium. I can do some more research looking at that picture.
In the final picture, are we sure that the 301 and the 121 aren't Azimuths? That would make logical sense since 301 - 180 = 121. It's probably been in use for some sort of surveying of sorts.
Looks like the city circled (picture #6) is Thionville/Yutz which had an airfield built by the US in Nov 1944. Maybe it was being built when this map was in use