her director, i would help with this however, i am a bit drunk right now but i can assure you hexane will not work.
i shall give more explicit details when i am sober.

it works but not as well as diethyl ether ether holds the no2/no3 gas complex very well
the addition should be done so the the h2so4 is dripped below the organic phase to avoid polymerization of the alkene.
and you are absolutely right about the ether and cystal formation.
nice to have a trained chemist here, a breath of fresh air you are.
also when you quench the psudonitrosite with a base to make the nitro alkene acidify it quickly (as soon as it goes into solution) because the base will cause scission at the benzylic carbon.
speed and temperature are key.  

As I interpreted it, DOS was using nitrogen dioxide, bypassing nitrite.

You might be able to get nitrites by hydrolysing nitrosyl chloride, I guess.

i envisioned a concentrated solution of sodium nitrite with suspended iron filings that the 37%+ H2SO4 was added to dropwise. initially the NO2 formed would oxidize in the flask temporarily creating a vacuum so you would have to be sure of positive  gas flow before submerging the tube into the solution of diethyl ether and calamus oil (or distilled asarone) after there is flow it would be nearly all N2O3 gas with very little NO. ill have to draw up the lab setup idea i have for the production of pseudonitrosites and post it here in a little while. with the setup i had in mind the excess N2O3 would first be bubbled through sulfuric acid generating nitric acid and hydrogen sulfide which would then be bubbled through say an 8M solution of sodium hydroxide generating sodium nitrate and sodium sulfate, if anything made it past that the rest of the gases are passed through a drying tube packed with sodium hydroxide which would neutralize anything else so no hood would even be necessary. as for quenching the pseudonitrosite, that would be done in around a .5M to 1M sodium hydroxide solution chilled to 10*C or below. the quench should be instantaneous so the B-nitros would be filtered and rinsed with dilute hydrochloric or acetic acid, maybe even the dilute nitric acid made in the process along with the pseudonitrosite. followed by a recrystalization from boiling methanol to remove any traces of acid left over.

wizard your name aptly describes you.

id figure something like this using the same setup i posted earlier. it might be better on a smaller scale using 150ml-500ml flasks.  the first flask would be charged with dry sodium nitrite and 37%+ H2SO4 in the dropping funnel. as the acid is dropped in making NO and NO2 any nitrous acid formed between the gases and small amounts of water from the H2SO4 should stay in that flask allowing fairly dry gases to cross over to the second flask containing the previously dried ether/oil mix (over anhd. MgSO4) which is placed in a cooling bath of ice and calcium chloride which will allow it to get to -40*c. at that temperature the dry NO/NO2 complex will condense into anhydrous nitrous acid (N2O3) dissolved in the ether solution. making concentrations much higher and even through out the solution more so than anyone could hope to achieve if the ether/oil was floating on an aqueous NaNO2/H2SO4 solution. the reaction to the pseudonitrosite should proceed rather quickly with heavy precipitation of product, even a dropping funnel could be added to the second flask to make additions of more asarone as the asarone in solution is used up. from there the un-used gases would be neutralized as they pass through the rest of the setup. the pseudonitrosite would be vacuum filtered while cold and ground and rinsed with fresh cold ether before being cautiously added to a .5M NaOH solution chilled to 5*C or less. instantaneous reduction to the B-nitro should occur resulting in bright yellow/orange crystals (as well as day-glo green under UV). filter it fast to get it away from the base and wash first with a 1M (5%) HCl solution chilled to 5*C then with cold water and finally with ice cold methanol (at least -10*C). the now clean acid free B-nitro would be recrystallized form boiling methanol for additional purity. from there dissolve 5g or so of your B-nitro in 200ml ethanol or methanol with 30ml 5M HCl. make up your amalgam (rinsing it clean before you toss it in the solution) i could see it taking about 20g maybe 30g but more could be made as backup. keep the temp right around 50*C or less. over the course of 1.5-2hr the solution should become clear as the B-nitro is used up, add more aluminum amalgam if it has not gone clear by 2hr.  cautiously add 2M NaOH to the solution to put it past neutral and filter out the aluminum gunk the best you can and then acidify it and extract with ether to remove trace amounts of unused B-nitro. re-basify and extract with 3 100ml portions chloroform or TCE dry the chloroform extracts and gas with HCL or acidify with 37% H2SO4 dropwise. i cannot speculate on yields at this time because it is untested for now... but i would expect at least 50% or better

Your worried about contact of H₂SO₄ yet I have already explained how you can form your nitros acid solution prior to stirring with the oil/ether mixture. No Sulfuric acid needed only reduction of nitric acid, prior to the addition of the alkene, using metabisulfites. Its a sure shot for GABA Diazotation and its to simple to not attempts a small scale proof of concept for yourself before attempting anything more complicated such as gasous N₂O₃.

I am also confused as to why the need for the Fe on the nitrites. What does this serve?

You said Nitrites in your post and I assumed thats what you ment so when I get time I will correct it.

The low yeilds I believe are due to hinderence and not so much being a biphasic mixture. If it where due to the methods then it would not have acceptable yeilds on other substrates.

several papers i have read all used 1,1,1-TCE to pull the freebase out of the Hg/Al dried it and salted with consentrated sulfuric acid. the only one i came across that used HCl was shulgins method where he stripped the solvent under vacuum dissolved the freebase in IPA and neutralized with HCL before adding 1500ml or so of ether to the solution before it crashed out as an oil that upon stirring crystallized.