Re Vehicles : the only vehicles that can transition from planet to space, when fitted with thruster, are Sleipnirs and Quads and ofc the rather more expensive warp capable quads such as the Equus and Firebird.
Re Lootables : Items which are placed in the inventory tabs 'Materials' and 'Mined Resources' are lootable whether stackable or not. This includes items inside boxes, vases, cases or vehicle inventories, that would normally appear in these tabs, so always double and triple check what you are carrying, and scroll right to the bottom of each tab as sometimes MA slides things down the page.
Re Travel in space: It is not necessary to zig-zag across space. It is however advisable to leave the area at the spacestation with caution in case you are observed by a pirate or their helper. Set off in a direction at variance with your intended destination, then once out of sight you change direction and elevation. Once you have achieved the elevation you require use the 'align horizontal' icon to ensure you do not continue to climb/dive, as space is 3D but in a box, and if you hit top/bottom/sides you will get the message 'Cannot enter deep space' If this happens back off, level out and turn back onto required direction.
and yes as stated above.: don't forget to carry a repair tool RK-0 and at least 5 ped TT of welding wire so you can repair ship if you are blown up by a pirate or a space mob.
Space mobs (yes they are huntable but tough), as you travel more you will encounter these, and most are in specific locations which are known as training grounds, the locations of these will appear on your space map only after first visit to each location.
http://kronan-ms.info/space-entities/