The short answer is no. When You enter the a portal from the nether, on your way to the overworld, Minecraft calculates the primary portal coordinates with this generalized equation:
{X, Y, Z} → {floor(X) × 8, Y, floor(Z) × 8}
The game then checks for an active portal in a 128 block radius around that location. Given your nether portal coordinates:
X: -70; Y: 72; Z: -139
Your overworld portal must be within the following horizontal bounds:
X = -688, -432
Z = -1240, -984
Remember, any overworld portals within 1024 blocks of each other will link to the same nether portal, because 1024 blocks in the overworld = 128 blocks in the Nether, and the game checks for portals in a radius of 128 blocks.
If you build a new nether portal at the blaze farm and destroy your old portal, your main base portal will probably link up to your blaze farm. However, when you attempt to go back to the overworld, Minecraft will look for a portal within the above bounds and create a new one if it doesn't find one.
Your best option is probably to build a rail line from your current portal to the blaze farm. Ghasts can destroy any block with a blast resistance below 20.17, but they won't shoot at you without a line of sight, so you can make an inexpensive safety-tunnel around your rail line with pure Netherrack.
You can also build a more scenic tunnel with stone, glass, leaves, fences, etc, since Ghasts cannot "see" through transparent blocks.
In singleplayer, the nether is not loaded by default, so any pigmen (or other mobs) that spawn in the overworld and wander through the portal don't move or count towards the mob count anymore, until you enter the nether. This is one way to get around the cap for naturally spawned mobs, storing the mobs in the nether until it is time to kill them.
This can lead to dangerous (for your computer/framerate) amounts of mobs in the area around the portal once you do enter the nether though, so if it is not part of your design, turn off your portal before afking. Doing so will also keep the pigmen from spawning in the overworld.
Best Answer
No. The world border is the same in both the Overworld and the Nether, so you can access the same amount of land. Although, in normal gameplay, this will not be noticeable(
60000000blocks is a lot!). Executing/worldborder getin both dimensions returns the same result in both dimensions, even if you change the worldborder. Both dimensions are the same size, and big enough to the point that no survival player will(probably) ever get there.