Vaderisnothayden said:
I read on imdb that in he 1981 reissue of the first film "Close the blast doors" was added and "Blast it Biggs" was changed to "Blast it Wedge". Is this true?

No, it's not true. People are confusing things about the mono sound mix and posting erroneous information to the IMDB. "Close the blast doors" and "Blast it, Wedge" were exclusive to the mono mix and were not added to any other versions of the film at the time. "Close the blast doors" was eventually added to the Special Edition in 1997; "Blast it, Wedge" was banished to obscurity.

Vaderisnothayden said:
In the showings 1981-85 was any particular mix (mono, 70mm, 35mm) dominant? Were those mono line changes dominant?

35mm Dolby Stereo was the most prominent, but there were at least some 70mm presentations too. As SilverWook already suggested, Dolby sounds systems had become more prevalent so there were few (if any) 35mm mono prints still circulating.

Vaderisnothayden said:
I read on imdb that the two non-mono mixes were updated with the "A New Hope" name and the mono was not.

This is not known for sure, but I wouldn't be surprised if at least some mono prints were updated too. Of interest is the fact that the mono mix was televised in the UK throughout the 80's and it did have the updated crawl.

Vaderisnothayden said:
Would I be right in saying the 1995 vhs's audio is the 1985 mix made for the 1985 vhs?

No, that's incorrect. The 1995 "THX" sound mix was a new mix created for the 1993 Definitive Collection and was also used for the 1995 home video release. This new sound mix was supposed to incorporate the best elements of the original three mixes.

Vaderisnothayden said:
So if I'm right, that's what lines are in the 1985 mix. Basically the non-mono version plus the tractor beam line.

That's correct. The 1985 home video sound mix is basicaly the same as the '77 Dolby mix with the addition of Threepio's tractor beam line.