I think getting Carista is the right first step. It might be that your just unlucky with regen timing. Carista gives you the option to trigger a regen when you want, so if you are 30 miles from home with nearly 30g of soot and know your next journeys will be short ones, just regen.
How old is the van?
DPF removal is illegal, but some do it. Not sure the EGR is at the same level of naughtiness, but others will confirm. I’m no fan of the EGR, but by removing it your combustion and likely engine temps will go up, although I’m not sure that would matter if you’re UK based.
Reputable map and dpf removal may not go hand in hand.
If you think your current map is not great, maybe take it to VW and have them flash the latest software. I believe it manages regen sand adblue issues better, then see how it is for a while.
I’m sure far more knowledgable members will be along to comment, or correct me