+1 for pictures.
I would avoid the remap - it killed my clutch (VRS 6 Speed) although you have a new one courtesy of your broken gearbox
Also it costs the same as at least 3 tanks.
I found no difference on additives with my PD130 but my driving is mainly town only so that might have made a difference.I blocked the upper grill with one from Superskoda (after trying tape / plastic) and the lower one - fast warmups definitely.
One other mod is ventectomy - block the vent which makes filling up a pain. Some claim it means you will over fill and spill Diesel but it never happened for me, the paintwork was always clean afterwards.