Don't use filtrete filters - they are highly restrictive. Use a simple fiberglass filter or, if you want more filtering capability use a 4"/5" pleated media filter. Honeywell make them to fit into the typical 1" return grill, or install a filter cabinet in your return duct.

You were right to use merv 8,for all the reasons you named. If the filter buckled due to being covered in dirt/lint,replace it with another merv8 and check it on a weekly basis. The filter is catching dirt/lint instead of recirculating it like fiberglass does. It will get better and you will notice less dust on furniture. To give you the "BEST"advice,I need to know,how many in house,how many are less than 20 years old,how many work in a dirty inviroment,how many ingage in hobbys that get's them dirty and what kind of pets in house. There's possible construction issues but occupants is the place to start. BTW,merv 8 should cost no more than $4 each in case of 10,$5 bought singly.

I prefer a 4-5" pleated media filter cabinet mounted at return end of furnace...MERV 10 is fine...better protection of evap coil, blower motor, and indoor air quality...lasts up to one year before changeout is necessary...but if you must use 1" filters at the returns, use the pleated media variety, not the fiberglass models.

IMO

Filtration purpose is more or less to keep equipment clean, however because of the allergy crowd filter companies have gotten into the lucrative high end filter market. The reason for it is due to the repetitive nature of having to replace the filter over the course of a month in most cases. The dirtier the environment the more frequently the filter(s) will need to be changed.

Low end see thru filters only stop the big stuff and smaller particles make there way to blower motor, Evaporator coil and eventually washed into the condensate drain if it doesn't stay stuck to the Evaporator coil.

The dust in the air is nutrient rich and if this makes it to the Evaporator coil you have all the necessary ingredients to produce mold. (Damp, Dark, Cool and something to feed on--- mold doesn't feed on metal and plastic)

Air in equals air out.... a blower motor can not supply air thru duct system that it can not draw thru the return. If you block or restrict air flow at the filter, you reduce air thru the supply vents. This will drive up what is called 'static pressure' within the duct system. The higher the static pressure, the faster and more likely equipment will fail.

So if your air return is undersized, like many are, you are left with the decision of using a restrictive filter that may cause more harm than good or using a cheaper filter that will allow a certain amount of dust thru it, that will eventually cause maintenance issues and or failures as well.

I've taken the time to explain this as best as possible in a forum board setting, you may have to 'read' this slowly to fully understand what I am saying here. This is why every HVAC system is different: "DESIGN".

You stated the filter buckled. Was it very dirty after one month, or did it bend due to the force of the air?

What are the dimensions of your 1 inch filter? Do you know the size of your furnace and AC?