Colour B4 on an ombré?

Your base is still not light enough for cool toned pastels, sorry. You want a colour similar to my avatar pic ideally, with very minimal yellow tones.(Obviously my hair was toned in that pic, it is a light creamy blonde, the elusive 'inside of a banana' colour underneath.)
You don't need a perfect base for pastel purples, as the dye will tone any remaining yellow. Plus your boyfriends colour isn't really pastel, but more of a mid-tone, which is easier than very light shades.
Bleach damage (all chemical damage) is permanent and cumulative. You cannot repair it, only mask it, so even fairly gentle processing can be the straw that breaks the camel's back on previously processed hair, no matter how healthy it feels.
The only way to know for certain is to try on a strand test. Ideally on a strand still attached to your head, so you can see how it stands up to regular wear and tear. Often the full extent of the damage doesn't start to show for several weeks.

Useful information Wicked Pixie thank you! May try the strand test much later down the line and see how it fairs.
I think that pic makes his hair appear slightly darker than it is but, yes, its not truly a pastel. Would you say I'm in the ballpark for a mid-lilac like this or will additional lightening be necessary? (beyond removing the red pigment with Decolour Remover.)

It is so hard to tell from pics, but your hair looks too warm, too much orange still. Purple will only tone yellow, so i don't think you are quite light enough yet

It has re-oxidised a fair bit today guys. More so in life than this photo shows but its reasonably apparent if you compare the pic to yesterdays  *ott*
I've followed the instructions to a T twice now and have gotten a fair degree of reoxidisation, I was not sure the first time as there was so much colour build up but this time its a certain. Shame as I was thrilled last night! I've added no additional products to the hair and today only used baby shampoo (the darkening occurred prior to the shampoo'ing.) This is exhausting! Any tips folks? 🙂

All I can suggest is rinsing it with as hot as you can stand water, for as long as you can possibly stand.

All I can suggest is rinsing it with as hot as you can stand water, for as long as you can possibly stand.

I went in with Decolour again  *devil* Here's a funny story for you....

14 minutes of rinsing under hot water in the shower....blow dried it 90%....back in the shower for another 10 minutes of rinsing. Our shower cubicle is rather small and its hot today in Old Blighty. Ended up moaning in discomfort from the heat with my head under the shower, my naked bum sticking out the cubicle trying to keep at least some part of my body from overheating and other half laughing at the comedy while he timed the whole affair  *puzz* :laugh:

I think we can all conclude that if my hair reoxidises again the next logical step will be just leaving it be to grow out. Hopefully it won't, It got it a wee bit lighter the past two times even with re-oxidisation and this amount of rinse time went above and beyond what the product calls for so crossed fingers. It looks good at this stage but, of course, it always does after I use the product! Will have to wait 2-3 days to see if re-oxidisation occurs.

EDITED TO ADD: Should I shampoo it every day for 2-3 days with clarifying shampoo to further prevent reoxidisation and is it acceptable to use a 'cone free conditioner after lest it turns to straw? Kind thanks!